docs: add the link of ESLint example to guideline (#73491)
## Summary
Add
[`with-eslint`](https://github.com/vercel/next.js/tree/canary/examples/with-eslint)
example link to
[adding-examples.md](https://github.com/vercel/next.js/blob/canary/contributing/examples/adding-examples.md)
for convenience.
### Improving Documentation
- [x] Run `pnpm prettier-fix` to fix formatting issues before opening
the PR.
- [x] Read the Docs Contribution Guide to ensure your contribution
follows the docs guidelines:
https://nextjs.org/docs/community/contribution-guide
