Mkdocs-literate-nav

* [Fix compatibility with MkDocs 1.5+](https://github.com/oprypin/mkdocs-literate-nav/commit/2c52c0cdea4994325926e653eeee2c5752882c2d)
* [Fix when markdown extensions is set to None](https://github.com/oprypin/mkdocs-literate-nav/commit/0825f8a683a27c13e738b6d7dd2d7b6c962d2a48)

* Allow specifying Markdown config: extensions, tab_length (15)
* Add type annotations according to mypy
* Drop Python 3.6

Features:

* Now you can use wildcards and directory cross-linking in `mkdocs.yml` `nav:` - 662c565ff0217d03274c62208d04bef6721033f2, 3e1879cba78356e400b0494428611e91d197180b
* Wildcards ending with a slash now select only directories - dd6b4027278ca174582c6aaecc7ddb49c2402ad1

Breaking changes:

* The default value of `nav_file` changed to SUMMARY.md, from index.md - e6fd5b1c4424460a540707d962b70094159dd933
* Nav files will not be picked up by wildcards - 37b7c230daffe28f3cf71161386afd7cef75b833

Semi-breaking refactors:

* Replace globbing implementation; remove glob2 dependency - 1b02eb7412666a2150338b78522b205d07f06a8d
* Require directories to have a trailing slash to be eligible for cross-linking - 81addd923c748412686170d84b0531ce1beb80ba
* Resolve wildcards and seen items depth-first - 3e1879cba78356e400b0494428611e91d197180b

Fixes:

* Fix special characters causing weird escape sequences - 740bb2a125a1a58b506aa788326292fb7a74ed2e
* Fix "implicit index" - f1bb432b89e1f02ed701cf18bac61dc78f46e961