This time as an EditorPlugin!
Improve rendering of inner area of MarginContainer
Decrease thickness and opacity of lines, and render margins as a rectangle rather than lines extending to the edges of the bounding box
Apply suggestions from code review
Co-authored-by: Tomasz Chabora <kobewi4e@gmail.com>
Use `get_margin_size`, change color of viz border, and trigger redraw on MarginContainer's draw signal
Replace text for add/close buttons with icons, remove theme preview custom minimum width, fix "Manage Items" window size in single-window mode and editor window at minimum size. Also theme preview tab looks like scenes tab.
This allows to reduce minimum size of `ThemeEditor`, improving (partially fixing) the use of non-standard editor layouts (for example, 2 columns for left dock and 1 column for right dock) without panels pushed out of screen.
