New editor UI

[aleokdev]

WIP. Replaces the old macroquad-based UI with egui.

[zicklag]

Hey @aleokdev thanks for working on this!

I wanted to do some work on the maps, and the current editor's object placement snapping was bugging me, so I wanted to try this out. Since I needed to be able to place critters, I ended up rebasing your branch on top of the latest master branch, and I pushed it to my fork: https://github.com/zicklag/FishFight/tree/new_editor_ui.

If you continue working on this, I just wanted to let you know, in case you wanted to use it as reference to get up-to-date with master later.

[aleokdev]

Cool, thanks! Just letting you know that the reason I was idle was because I was waiting for abraxas to finish his big refactor so that I could integrate the changes.

[erlend-sh]

Due to the #466 Bevy Rewrite this work is defunct, but the contribution is recognized and remains appreciated! 🙏