add README

Signed-off-by: Teo Koon Peng <[email protected]>

Author: koonpeng

diagram-editor/README.md

@@ -1,4 +1,8 @@
-# Rsbuild project
+# bevy_impulse_diagram_editor
+
+![](./docs/assets/diagram-editor-preview.webp)
+
+This contains a SPA React web app to create and edit a `bevy_impulse` diagram and an axum router to serve it.
 
 ## Setup
 
@@ -8,22 +12,59 @@ Install the dependencies:
 pnpm install
 ```
 
-## Get started
+## Embedding the Diagram Editor into a `bevy_impulse` app
+
+The frontend is built using `rsbuild` and embedded inside the crate. The library exposes an axum router that can be used to serve both the frontend and backend:
+
+```rs
+use bevy_impulse_diagram_editor::{new_router, ServerOptions};
+
+fn main() {
+  let mut registry = DiagramElementRegistry::new();
+  // register node builders, section builders etc.
 
-Start the dev server:
+  let mut app = bevy_app::App::new();
+  app.add_plugins(ImpulseAppPlugin::default());
+  let router = new_router(&mut app, registry, ServerOptions::default());
+  let listener = tokio::net::TcpListener::bind(("localhost", 3000))
+      .await
+      .unwrap();
+  axum::serve(listener, router).await?;
+}
+```
+
+To omit the frontend and serve only the backend API, disable the default features:
+
+```toml
+[dependencies]
+bevy_impulse_diagram_editor = { version = "0.0.1", default-features = false }
+```
+
+See the [calculator demo](../examples/diagram/calculator) for more examples.
+
+## Local development server
+
+Normally the web stack is not required by using this crate as a dependency, but it is required when developing the frontend.
+
+Requirements:
+
+* nodejs
+* pnpm
+
+First start the `dev` backend server:
 
 ```bash
-pnpm dev
+pnpm dev:backend
 ```
 
-Build the app for production:
+then in another terminal, start the frontend `dev` server:
 
 ```bash
-pnpm build
+pnpm dev
 ```
 
-Preview the production build locally:
+When there are breaking changes in `bevy_impulse`, the typescript definitions need to be regenerated:
 
 ```bash
-pnpm preview
+pnpm generate-types
 ```