* Improve custom admonitions documentation

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci



* Apply suggestions from code review

Co-authored-by: Chris Holdgraf <choldgraf@gmail.com>

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Chris Holdgraf <choldgraf@gmail.com>