Adds a dependency array system to `recv_glib` which internally clones the passed deps and then passes by reference to the callback.
This cleans up a lot of the big `{}` blocks full of `widget.clone()` and removes a lot of boilerplate. Yay!
Rewrites the desktop file parser code and image resolver code to introduce caching system and make fully async. They should be much faster now.
BREAKING CHANGE: The `icon_theme` setting has been moved from per-bar to top-level
