(examples): fix missed peer dependencies (#26069)
Fixes some examples from #25854
- with-kea [live demo](https://stackblitz.com/github/akellbl4/next.js/tree/examples/missed-peer-deps/examples/with-kea)
- with-mobx [live demo](https://stackblitz.com/github/akellbl4/next.js/tree/examples/missed-peer-deps/examples/with-mobx)
- with-mobx-react-lite [live demo](https://stackblitz.com/github/akellbl4/next.js/tree/examples/missed-peer-deps/examples/with-mobx-react-lite)
- with-mobx-state-tree [live demo](https://stackblitz.com/github/akellbl4/next.js/tree/examples/missed-peer-deps/examples/with-mobx-state-tree)
## Documentation / Examples
- [x] Add the StackBlitz button
- [x] Make sure the linting passes
