Bump pymdown-extensions from 10.15 to 10.16.1 (#278)

Bumps [pymdown-extensions](https://github.com/facelessuser/pymdown-extensions) from 10.15 to 10.16.1.
- [Release notes](https://github.com/facelessuser/pymdown-extensions/releases)
- [Commits](facelessuser/pymdown-extensions@10.15...10.16.1)

---
updated-dependencies:
- dependency-name: pymdown-extensions
  dependency-version: 10.16.1
  dependency-type: indirect
...

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