Add internal docs how to use this repo

DEVELOPMENT.md

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+# Development process
+
+## Rust
+
+### Binaries
+
+Directory **`src/bin`** in Rust crate have a special meaning. Each **`*.rs`** file or directory
+(with **`main.rs`**) is a binary that can be executed with:
+
+```
+cargo run --bin <binary_name>
+```
+
+For example:
+
+```
+cargo run --bin package_for_relase
+```
+to run **`./src/bin/package_for_release/main.rs`**.
+
+or
+
+```
+cargo run --bin main_process
+```
+
+to run **`./src/bin/main_process.rs`**
+
+
+To run binary from specific create you need to run the command from that crate directory.
+
+#### `live_compositor` create (root)
+
+- `package_for_relase` - builds release binaries that can be uploaded to GitHub Releases
+- `main_process` - main binary to start standalone compositor
+- `process_helper` - starts secondary processes that communicate with `main_process`
+  to enable web rendering with Chromium
+
+### `integration_tests` crate
+
+- `play_rtp_dump` - helper to play RTP dumps generated in tests from **`./integration_tests/src/tests`**.
+  Useful to verify if new tests generated correctly or to see what is wrong when test is failing.
+- `generate_rtp_from_file` - helper to generate new input files that can be used for new tests in
+  **`./integration_tests/src/tests`**.
+
+### `generate` create
+
+This is crate when we keep most of our utils that generate something in repo:
+
+- `generate_docs_examples` - generates WEBP files with examples for documentation.
+- `generate_docs_example_inputs` - helper for `generate_docs_examples` (generates inputs for that binary).
+- `generate_from_types` - generate JSON schema from `compositor_api` types. It needs to be called every
+  time API is changed and regenerated file needs to be committed. (It also generates Markdown docs, but
+  this will be soon removed)
+- `generate_playground_inputs` - TODO
+
+### Examples
+
+TODO
+
+### Tests
+
+We have 3 main types of test:
+- Small amount of regular unit tests spread over codebase.
+- Snapshot tests that render specific image and save them as PNG.
+  - Generated images are located in **`./snapshot_tests/snapshots/render_snapshots`** directory.
+  - JSON files representing tested scenes are in **`./snapshot_tests`** directory
+  - Actual Rust tests are in **`./src/snapshot_tests`**.
+  - For example:
+    - Test is located in **`./src/snapshot_tests/view_tests.rs`**
+    - Test is rendering scene described by **`./snapshot_tests/view/border_radius.scene.json`**
+    - Test is rendering output (or comparing with the old version) to
+      **`./snapshot_tests/snapshots/render_snapshots/view/border_radius_0_output_1.png`**
+- End-to-end tests that are basically snapshot tests, but compare entire videos.
+  - Generated stream dumps are located in **`./snapshot_tests/snapshots/rtp_packet_dumps`** directory.
+  - Tests are implemented in **`./integration_tests/src/tests`** directory.
+  - Some of the test here might be fragile if running along a lot of CPU intensive
+    tasks. That is why **`./.config/nextest.toml`** is limiting concurrency of some tests on CI.
+
+Initially when setting up the repo, or when checking out different branch you need to update
+submodule to the correct version by running
+```
+git submodule update --init --checkout
+```
+
+> Carefully read output of the command to make sure it worked. It will fail if you have uncommitted
+changes in the **`./snapshot_tests/snapshots`** directory.
+
+To run all test run:
+
+```
+cargo nextest run --workspace --profile ci
+```
+
+If you don't have `nextest` installed you can add it with;
+
+```
+cargo install cargo-nextest
+```
+
+To run specific test add name of the function or crate at the end:
+
+e.g.
+
+```
+cargo nextest run --workspace audio_mixing_with_offset
+```
+
+will run a test from **`./integration_tests/src/tests/audio_only.rs`**
+
+#### Updating snapshots
+
+By default, snapshot tests generate new output and compare with the old version committed
+to repo. If version in repo is different or missing then tests will fail.
+
+To generate snapshots for new tests, or update those that should change you need to enable
+`update_snapshots` feature when running tests. It is recommended to only run that command
+for specific tests, especially **`./integration_tests/src/tests`**
+
+e.g.
+
+```
+cargo nextest run --workspace --features update_snapshots audio_mixing_with_offset
+```
+
+will run a test from **./integration_tests/src/tests/audio_only.rs** and if output changed the update the snapshot.
+
+If you made changes that modify the snapshot:
+- Create PR in https://github.com/membraneframework-labs/video_compositor_snapshot_tests repo.
+- Create PR in live compositor repo with link to the snapshot repo PR.
+- Merge them together.
+
+## TypeScript SDK
+
+### Packages
+
+- `live-compositor` - React components and common API types. (analog of `react` package).
+- `@live-compositor/core` - Base implementation that is used by packages like `@live-compositor/node`.
+- `@live-compositor/node` - Node.js SDK for compositor  (analog of `react-dom` for Node.js)
+- `@live-compositor/web-wasm` - Browser SDK for compositor that includes compositor compiled to WASM (analog of `react-dom` for Node.js)
+- `@live-compositor/browser-render` - Rendering ending from LiveCompositor compiled to WASM.
+  - Run `pnpm run build-wasm` to build WASM bundle from Rust code
+  - Run `pnpm run build` to build JS code (WASM has to be build earlier, or use `build:all` in root directory to build everything)
+
+### API compatibility
+
+> WARNING this is the goal, it is currently not true.
+
+SDK should be always compatible with version of code from the repo. If you are changing API the changes to SDK should land in the same PR.
+
+### Examples
+
+To bootstrap repo run:
+
+```
+pnpm install && pnpm build:all
+```
+
+After that you can run only `pnpm run build` to rebuild if Rust code did not change.
+
+#### Node.js: **`./ts/examples/node-examples/`**
+
+To run example **`./ts/examples/node-examples/src/simple.tsx`**, go to **`./ts/examples/node-examples`** and run:
+
+```
+pnpm run ts-node ./src/simple.tsx
+```
+
+> TODO: instructions below needs to be automated to build Rust automatically and point examples to this binary
+
+To run Node.js example against Rust code from the repo you need to in the root directory run:
+
+```
+cargo build -r --no-default-features
+export LIVE_COMPOSITOR_PATH=$(pwd)/target/release/main_process
+```
+
+#### Web WASM: **`./ts/examples/vite-browser-render`**
+
+Run
+
+```
+pnpm run dev
+```
+
+Open `localhost:5173` in the browser
+
+If Rust code changes you need to rebuild WASM with `pnpm run build-wasm`.