chore: make people aware of synced content

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,9 @@
+### A note on documentation PRs
+
+If this is a documentation PR (i.e. changing content within `apps/svelte.dev/content/docs`), then this is the wrong repository to make those changes. The content in this folder is synced from other repositories. Therefore, these changes should be made in their respective repositories (at https://github.com/sveltejs/svelte or https://github.com/sveltejs/kit, or example).
+
+### Before submitting the PR, please make sure you do the following
+
+- [ ] It's really useful if your PR references an issue where it is discussed ahead of time.
+- [ ] Prefix your PR title with `feat:`, `fix:`, `chore:`, or `docs:`.
+- [ ] This message body should clearly illustrate what problems it solves.

apps/svelte.dev/README.md

@@ -2,6 +2,16 @@
 
 This is the app behind [svelte.dev](https://svelte.dev), the official Svelte site.
 
+## Documentation PRs
+
+If you're creating a documentation PR, make sure you're targeting the right repository. More specifically, changes to content within `apps/svelte.dev/content/docs` are synced from other repositories, and documentation changes within those folder should therefore be made in those repositories:
+
+- `docs/svelte` -> https://github.com/sveltejs/svelte
+- `docs/kit` -> https://github.com/sveltejs/kit
+- `docs/cli` -> https://github.com/sveltejs/cli
+
+The tutorial, blog and examples are maintained within this repository.
+
 ## Development
 
 ### Tutorial