Bump tsdown from 0.21.7 to 0.21.8 in /bindings/js

Bumps [tsdown](https://github.com/rolldown/tsdown) from 0.21.7 to 0.21.8.
- [Release notes](https://github.com/rolldown/tsdown/releases)
- [Commits](rolldown/tsdown@v0.21.7...v0.21.8)

---
updated-dependencies:
- dependency-name: tsdown
  dependency-version: 0.21.8
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]