fix: set npm homepage to aimock.copilotkit.dev (#105)

## Summary

npm shows `github.com/CopilotKit/aimock#readme` as the homepage because
there's no `homepage` field in package.json. Adds `"homepage":
"https://aimock.copilotkit.dev"` so npm links to the docs site.

Takes effect on next npm publish.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Author: jpr5

package.json

@@ -35,6 +35,7 @@
     "embeddings",
     "copilotkit"
   ],
+  "homepage": "https://aimock.copilotkit.dev",
   "repository": {
     "type": "git",
     "url": "https://github.com/CopilotKit/aimock"