Bump rollup from 4.20.0 to 4.21.0 in the npm group

Bumps the npm group with 1 update: [rollup](https://github.com/rollup/rollup).


Updates `rollup` from 4.20.0 to 4.21.0
- [Release notes](https://github.com/rollup/rollup/releases)
- [Changelog](https://github.com/rollup/rollup/blob/master/CHANGELOG.md)
- [Commits](rollup/rollup@v4.20.0...v4.21.0)

---
updated-dependencies:
- dependency-name: rollup
  dependency-type: direct:development
  update-type: version-update:semver-minor
  dependency-group: npm
...

Signed-off-by: dependabot[bot] <[email protected]>