Bump @stencil/core from 4.19.2 to 4.21.0

Bumps [@stencil/core](https://github.com/ionic-team/stencil) from 4.19.2 to 4.21.0.
- [Release notes](https://github.com/ionic-team/stencil/releases)
- [Changelog](https://github.com/ionic-team/stencil/blob/main/CHANGELOG.md)
- [Commits](ionic-team/stencil@v4.19.2...v4.21.0)

---
updated-dependencies:
- dependency-name: "@stencil/core"
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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