chore(deps): bump underscore and doctoc

Bumps [underscore](https://github.com/jashkenas/underscore) to 1.13.6 and updates ancestor dependency [doctoc](https://github.com/thlorenz/doctoc). These dependencies need to be updated together.


Updates `underscore` from 1.8.3 to 1.13.6
- [Release notes](https://github.com/jashkenas/underscore/releases)
- [Commits](jashkenas/underscore@1.8.3...1.13.6)

Updates `doctoc` from 1.4.0 to 2.2.1
- [Release notes](https://github.com/thlorenz/doctoc/releases)
- [Commits](https://github.com/thlorenz/doctoc/commits)

---
updated-dependencies:
- dependency-name: underscore
  dependency-type: indirect
- dependency-name: doctoc
  dependency-type: direct:development
...

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