Clicking component tag doesn't open file in local editor

Hey! I've been using react-grab and noticed that clicking the component tag/label in the floating selection box doesn't actually open the file in my editor.

After digging into the code, I found that `buildOpenFileUrl` redirects to `react-grab.com/open-file` instead of opening the file directly in the local editor. The file path is also relative (like `/src/App.tsx`) rather than absolute, which editors need.

I've put together a fix in #49 that:
- Uses editor URL schemes directly (supports VS Code, Cursor, WebStorm, etc.)
- Builds absolute paths using `__PROJECT_ROOT__` from Vite config
- Opens the file at the component's location
- Falls back to the original behavior if not configured

Would love to hear your thoughts!