Bump tslib from 2.6.3 to 2.8.1

Bumps [tslib](https://github.com/Microsoft/tslib) from 2.6.3 to 2.8.1.
- [Release notes](https://github.com/Microsoft/tslib/releases)
- [Commits](microsoft/tslib@v2.6.3...v2.8.1)

---
updated-dependencies:
- dependency-name: tslib
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]