Improve "loaded files" window

[CramBL]

When loading a huge amount of files the window should be scrollable, it isn't now, it's barely functional.

Something like this perhaps? https://github.com/emilk/egui/blob/master/crates/egui_demo_lib/src/demo/code_editor.rs

It dynamically adds a scroll bar when the window grows large enough.