UI element JS Classes

https://discord.com/channels/732325252788387980/734922093967310910/882979923483037696
@wyrmisis

I KEEP FINDING OUT ABOUT THINGS LIKE DIALOG AND CONTEXTMENU AND I REALLY WISH THESE UI ELEMENT CLASSES WERE LISTED SEPARATELY FROM SHEET/DOCUMENT/ETC CLASSES IN THE API DOCS

Let's fix this. cc @📰 Wiki Keepers

What are some of these UI element classes that could use a spotlight, and how can we make a useful wiki page introducing them?

Off the top of my head:
- Application
- Dialog
- FormApplication
- ContextMenu
- DragDrop?

We have wiki guides for several of these, but nowhere lists them all