Bump underscore and jsdoc-to-markdown

Bumps [underscore](https://github.com/jashkenas/underscore) to 1.13.6 and updates ancestor dependency [jsdoc-to-markdown](https://github.com/jsdoc2md/jsdoc-to-markdown). These dependencies need to be updated together.


Updates `underscore` from 1.8.3 to 1.13.6
- [Commits](jashkenas/underscore@1.8.3...1.13.6)

Updates `jsdoc-to-markdown` from 4.0.1 to 8.0.1
- [Release notes](https://github.com/jsdoc2md/jsdoc-to-markdown/releases)
- [Commits](jsdoc2md/jsdoc-to-markdown@v4.0.1...v8.0.1)

---
updated-dependencies:
- dependency-name: underscore
  dependency-type: indirect
- dependency-name: jsdoc-to-markdown
  dependency-type: direct:development
...

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

Author: dependabot[bot]