feat: add Grok authentication plugin with OAuth support

- Introduced a new Grok authentication plugin, including essential files such as main.ts, provider.ts, and resources.ts.
- Implemented OAuth2 device authorization flow in oauth.ts, allowing users to sign in with xAI.
- Added model discovery and quota management functionalities in models.ts and resources.ts.
- Created a JSON configuration file (plugin.json) for plugin metadata and permissions.
- Included SVG asset for the Grok icon.
- Developed comprehensive tests in grok_test.ts to ensure functionality and reliability of the plugin.

server/plugins/build-in/grok-auth/plugin.json

@@ -0,0 +1,17 @@
+{
+  "apiVersion": 1,
+  "id": "dev.cursorbyok.examples.grok-auth",
+  "name": "Grok",
+  "version": "0.1.0",
+  "author": "@leookun",
+  "minAppVersion": "0.1.0",
+  "icon": "assets/grok.svg",
+  "entry": "main.ts",
+  "permissions": {
+    "network": [
+      "auth.x.ai",
+      "api.x.ai",
+      "cli-chat-proxy.grok.com"
+    ]
+  }
+}