Python 3.7 is now end-of-life

See https://github.com/executablebooks/markdown-it-py/releases/tag/v3.0.0 and https://github.com/executablebooks/mdit-py-plugins/releases/tag/v0.4.0

See https://github.com/tsutsu3/linkify-it-py/blob/main/CHANGELOG.md

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Chris Sewell <chrisj_sewell@hotmail.com>

See https://docutils.sourceforge.io/RELEASE-NOTES.html#release-0-20-2023-05-04

Co-authored-by: Chris Sewell <chrisj_sewell@hotmail.com>

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

Allow any value type (including dict, list, datetime, ...) and emit a `myst.substitution` warning for errors in resolving the substitution.

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Chris Sewell <chrisj_sewell@hotmail.com>

This commit makes the slug generation closer to GitHub,
in that, starting/ending whitespace will not be stripped.

For example, ``#  ` a` b `c ` `` will now correctly create the slug
`-a-b-c-` and not `a-b-c`

Co-authored-by: Chris Sewell <chrisj_sewell@hotmail.com>