Improve Github Action Workflow

@danielfdsilva spent time in #24 improving the GitHub workflow.
To keep our git history clean and make reviews easier, we should extract the workflow improvements into their own PR, based on the `develop` branch.

## GitHub Actions Workflow Updates (`.github/workflows/checks.yml`)

- [ ] Add descriptive header comments explaining the workflow purpose
- [x] Update trigger conditions:
- Remove `push` trigger on `main` branch
- Update `pull_request` types to: `opened`, `synchronize`, `reopened`, `ready_for_review`
- Add concurrency controls to cancel in-progress runs for the same ref
- [x] Update Node.js version strategy:
- Remove hardcoded `NODE` environment variable
- Use `node-version-file: '.nvmrc'` to read version from `.nvmrc` file
- [x] Update GitHub Actions to latest versions:
- `actions/checkout@v2` → `actions/checkout@v4`
- `actions/setup-node@v1` → `actions/setup-node@v4`
- `actions/cache@v2` → `actions/cache@v4`
- Remove deprecated `styfle/cancel-workflow-action` (replaced by concurrency)
- [x] Simplify cache key:
- Remove `cache-name` environment variable
- Use `${{ runner.os }}-build-${{ hashFiles('**/package.json') }}`
- [ ] Update job commands:
- Use explicit `yarn run lint` instead of `yarn lint`
- Use explicit `yarn run test` instead of `yarn test`
- Use explicit `yarn run build` instead of `yarn build`
- Fix build job step name: "Test" → "Build"
- [ ] Ensure `build` job depends on `test` job (not changed, but verify)

## References

- Original PR: #24
- Target branch: `develop`

## Notes

This is purely infrastructure/tooling changes with no functional code changes to the library itself.