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/deno.json

@@ -0,0 +1,13 @@
+{
+  "imports": {
+    "cursor-byok:plugin": "../../../src/plugin/sdk/plugin.ts",
+    "cursor-byok:provider": "../../../src/plugin/sdk/provider.ts",
+    "cursor-byok:model": "../../../src/plugin/sdk/model.ts",
+    "cursor-byok:resource": "../../../src/plugin/sdk/resource.ts",
+    "cursor-byok:protocol/openai-chat": "../../../src/plugin/sdk/protocol/openai_chat.ts"
+  },
+  "fmt": {
+    "lineWidth": 100,
+    "exclude": ["assets"]
+  }
+}