… utility

Add new extras entry point with optional tree-shakeable components:
- GridBackground: SVG grid background that aligns with GridLayout cells
- calcGridCellDimensions: Core utility for grid cell calculations

Based on PR #2175 by @nicosayer.

Also improves ESLint configuration:
- Add typescript-eslint for TypeScript file linting
- Add eslint-plugin-react-hooks
- Rename eslint.config.js to eslint.config.mjs for explicit ESM
- Ignore built example files
- Disable React Compiler rules (not using React Compiler yet)

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

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Change credit from @nicosayer to @dmj900501 who is the actual author
of the GridBackground feature PR.

* feat(extras): add wrap compactor for paragraph-style layouts

Implements wrap mode compaction where items flow left-to-right and wrap
to the next row, similar to words in a paragraph. When dragging:
- Moving an item earlier shifts other items right/down
- Moving an item later shifts other items left/up

This is a v2 reimplementation of the algorithm from PR #1773 by
@JohnThomson, adapted to the new composable Compactor interface.

Usage:
```tsx
import { wrapCompactor } from 'react-grid-layout/extras';
<GridLayout compactor={wrapCompactor} ... />
```

* fix(readme): correct attribution for PR #2175

Change credit from @nicosayer to @dmj900501 who is the actual author
of the GridBackground feature PR.