Set up versioned docs with mike

[afuetterer]

• mike delete --all --push --config-file=docs/mkdocs.yml -> resets the unversioned docs in gh-pages branch
• mike set-default --push latest --config-file=docs/mkdocs.yml
• message "outdated, see latest" ->
• set custom_dir: overrides, main.html, see: https://github.com/pinterest/ktlint/blob/master/documentation/release-latest/mkdocs.yml in docs/src
• mike deploy in ci
• Set site_url, see same page https://squidfunk.github.io/mkdocs-material/setup/setting-up-versioning/#stay-on-the-same-page-when-switching-versions

Refs:

• https://github.com/jimporter/mike
• https://github.com/jimporter/mike?tab=readme-ov-file#deploying-via-ci
• https://squidfunk.github.io/mkdocs-material/setup/setting-up-versioning/
• https://github.com/search?q=%22mike+deploy%22+path%3A%2F%5E.github%5C%2Fworkflows%5C%2F%2F&type=code
• https://github.com/pypa/hatch/blob/3f71b5ec9793ccae21c2fbb9a7b7aedbd08aeecb/hatch.toml#L83
• https://github.com/pypa/hatch/blob/3f71b5ec9793ccae21c2fbb9a7b7aedbd08aeecb/.github/workflows/docs-release.yml#L59