chore(examples): Update convex example

[thomasballinger]

This example is now very similar to the one at https://github.com/get-convex/convex-demos/tree/main/typescript which should make it easier to keep it updated moving forward.

Documentation / Examples

• Make sure the linting passes by running pnpm build && pnpm lint
• The "examples guidelines" are followed from our contributing doc

[balazsorban44]

Thanks, maybe it would make sense to deprecate this example and have a single README.md that points to the official example to avoid maintenance duplicate work. 🤔

[thomasballinger]

Thanks for merging @balazsorban44.

I really like using create-next-app to start new Convex projects and we hear the same from customers so we'd love to keep this in. If you're willing to keep merging updates, we'll keep them coming 😄