Static space build docs

docs/hub/spaces-config-reference.md

@@ -49,6 +49,12 @@ Value must be one of `"small"`, `"medium"` or `"large"`.
 Path to your main application file (which contains either `gradio` or `streamlit` Python code, or `static` html code).  
 Path is relative to the root of the repository.  
 
+**`app_build_command`** : _string_  
+For static Spaces, command to run first to generate the HTML to render. Use together with `app_file`. Example: `npm run build`. 
+
+Each update, the build command will run and the build output will be stored in `refs/convert/build`,
+which will be served by the Space. See an example at https://huggingface.co/spaces/coyotte508/static-vite
+
 **`app_port`** : _int_  
 Port on which your application is running. Used only if `sdk` is `docker`. Default port is `7860`.
 

docs/hub/spaces-sdks-static.md

@@ -6,7 +6,25 @@ Here are some examples of Spaces using custom HTML:
 
 * [Smarter NPC](https://huggingface.co/spaces/mishig/smarter_npc): Display a PlayCanvas project with an iframe in Spaces.
 * [Huggingfab](https://huggingface.co/spaces/pierreant-p/huggingfab): Display a Sketchfab model in Spaces.
+* [Diffuse the rest](https://huggingface.co/spaces/huggingface-projects/diffuse-the-rest): Draw and diffuse the rest
 
+## Adding a build step before serving
+
+Static Spaces support adding a custom build step before serving your static assets. This is useful for frameworks like Next.js, SvelteKit, and others that require a build process before serving. The build command runs automatically when your Space is updated.
+
+Add `app_build_command` inside the `YAML` block at the top of your Spaces **README.md** file, and `app_file`.
+
+For example:
+-  `app_build_command: npm run build`
+- `app_file: dist/index.html`
+
+Example spaces: 
+
+- [Svelte App](https://huggingface.co/spaces/julien-c/vite-svelte)
+- [React App](https://huggingface.co/spaces/coyotte508/static-vite)
+
+
+Under the hood, it will [launch a build](https://huggingface.co/spaces/huggingface/space-build), storing the generated files in a special `refs/convert/build` ref.
 ## Space variables
 
 Custom [environment variables](./spaces-overview#managing-secrets) can be passed to your Space. OAuth information such as the client ID and scope are also available as environment variables, if you have [enabled OAuth](./spaces-oauth) for your Space.