Mkdocstrings-crystal

* Eliminate unwanted whitespace around method headings - https://github.com/mkdocstrings/crystal/commit/93cc543c2cead0b3d95a222582561853dbc660e7, https://github.com/mkdocstrings/crystal/commit/31877a72fcdbec323fae735955ce64722a8517e9
* Restore bold around method names (gone since mkdocs-material version 8.1.5) - https://github.com/mkdocstrings/crystal/commit/6e890ae58028c7336fe4979eb7a4f47589342e72
* Workaround for args_html missing in Crystal when there are no args - https://github.com/mkdocstrings/crystal/commit/de9a1f08b103347614d0e1bb12b5aae4ba47905a

* Present constants' values - https://github.com/oprypin/mkdocstrings-crystal/commit/8d7fccb501daf4c0440c908c769ef1d09fa4e1c2

* (**Requires a style update**) Don't add square brackets to source links, leave it up to styling - https://github.com/oprypin/mkdocstrings-crystal/commit/cb1407e60e58028417595e20b85d64a108904bd3

* Log forgotten items in debug mode (`mkdocs build -v`) - https://github.com/oprypin/mkdocstrings-crystal/commit/41beffaa214f05b544bd3535c8bab0e278d042c1

* Item API tweaks

First release that doesn't have unreleased dependencies 🎉

* Move deduplicate_toc to a separate Markdown extension - https://github.com/oprypin/mkdocstrings-crystal/commit/d575e474aa218aa1adfc773d1890cad39fb9ac8a
* Define an API for doc items, not to expose raw JSON data
(current use is https://github.com/oprypin/mkdocs-gen-files)
* Linkify types in function args (requires Crystal **>** 0.35)
* Linkify aliases (requires Crystal **>** 0.35)

* Fix a bug where a filtered type couldn't lookup types under it
* Fix and refactor handling of Locations (prefers Crystal **>** 0.35)
* Bugfix for mislabeling alias definitions

* Drop Python 3.6