Bump readonly from 0.2.7 to 0.2.12

Bumps [readonly](https://github.com/dtolnay/readonly) from 0.2.7 to 0.2.12.
- [Release notes](https://github.com/dtolnay/readonly/releases)
- [Commits](dtolnay/readonly@0.2.7...0.2.12)

---
updated-dependencies:
- dependency-name: readonly
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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