docs: add bot discovery endpoint to getting started guide (#4570)

### Description

This PR adds documentation for the bot discovery endpoint to the Getting
Started guide. The `/.well-known/agent-metadata.json` endpoint exposes a
bot's identity metadata (username, display name, description, avatar) in
a standardized format, allowing bot directories and discovery services
to automatically index and display available bots.

### Changes

- Added "Add Bot Discovery Endpoint" section to
`packages/docs/build/bots/getting-started.mdx`
- Positioned the new section after project initialization and before
environment configuration
- Included clear code example showing how to implement the endpoint in
`src/index.ts`
- Added explanation that this endpoint is required for bot
discoverability

### Checklist

- [x] Documentation updated where applicable
- [x] Changes adhere to the repository's contribution guidelines
- [N/A] Tests added where required (documentation-only change)

Author: Crisvond-hnt

packages/docs/build/bots/getting-started.mdx

@@ -64,6 +64,19 @@ cd my-bot
 bun install
 ```
 
+### Add Bot Discovery Endpoint
+
+Open `src/index.ts` and add this route after the `/webhook` route:
+
+```ts
+// After your /webhook route
+app.get('/.well-known/agent-metadata.json', async (c) => {
+  return c.json(await bot.getIdentityMetadata())
+})
+```
+
+This endpoint is **required** for bot directories to discover and index your bot. After deploying your bot, go to the [developer dashboard](https://app.towns.com/developer/dashboard) and click the **Boost** button to submit your bot for indexing.
+
 ### Configure Environment
 
 Copy the `.env.sample` file in your project root: