docs: add a real-world example for a third-party grid (AG Grid or TanStack Table)

[rickcedwhat-ai]

What

Add a worked example to the docs showing playwright-smart-table wired up to a real-world table library that isn't covered by the existing MUI DataGrid playground.

Good candidates: AG Grid Community, TanStack Table, or Handsontable — all widely used in QA contexts.

Why

The existing playground uses MUI DataGrid and the generic HTML table. Users on other grids have to figure out config themselves. A single additional example (even a minimal one) dramatically lowers the barrier.

What makes this a good first contribution

You don't need to understand the source code. If you already use AG Grid or TanStack Table with Playwright, you likely have the setup already. The contribution is:

1. A small playground page (can follow the pattern of playground/src/ pages)
2. A matching docs page (docs/examples/ag-grid.md or similar) showing the config snippet
3. Opening a PR linking back to this issue

No deep TypeScript knowledge required — this is configuration and documentation work.

Notes for the contributor

• Look at the existing MUI DataGrid integration under tests/integration/ and playground/ for the pattern to follow
• Don't worry about adding a full CI test suite for the new grid — a docs example + playground page is enough for a first PR
• Ping the maintainer on the PR if you want guidance on the config

Not doing this ourselves

Leaving this open for a community contributor who already uses one of these grids.