Add avatar support for codeberg in git blame (#10991)

Release Notes:

- Added support for avatars in git blame for repositories hosted on
codeberg

<img width="1144" alt="Screenshot 2024-04-25 at 16 45 22"
src="https://github.com/zed-industries/zed/assets/43210583/d44770d8-44ea-4c6b-a1c0-ac2d1d49408f">

Questions:
- Should we move git stuff like `Commit`, `Author`, etc outside of
hosting-specific files (I don't think so, as other hostings can have
different stuff)
- Should we also add support for self hosted forgejo instances or should
it be a different PR?

crates/util/src/util.rs

@@ -1,5 +1,7 @@
 pub mod arc_cow;
+pub mod codeberg;
 pub mod fs;
+mod git_author;
 pub mod github;
 pub mod http;
 pub mod paths;