Feature/568 build wasm from cargo

[ja573]

• Removes the need to run wasm-pack before cargo build, i.e. cargo build can build the wasm target by making it a requirement of thoth-app-server through the custom build script thoth-app-server/build.rs
• Replaces wasm-pack and rollup with trunk, wich has its build configuration defined in thoth-app/Trunk.toml. By not bundling the app with rollup we can also get rid of node/npm as build dependencies
• Optionally load env variables from .env before building thoth-app and thoth-export-server, to eliminate the need to manually load env vars before running cargo build, cargo test, etc.