Add display-mode: window-controls-overlay

[meduzen]

Add support for @media (display-mode: window-controls-overlay) in:

--media.scss/src/variables/_ui.scss

Lines 4 to 7 in f247389

	@custom-media --minimal-ui (display-mode: minimal-ui);
	@custom-media --fullscreen (display-mode: fullscreen);
	@custom-media --standalone (display-mode: standalone);
	@custom-media --browser (display-mode: browser);

Read links below and understand it, then find relevant names, like maybe --window-controls or --window-controls-overlay.

References:

• Customize the window controls overlay of your PWA's title bar
• Display content in the title bar
• Window Controls Overlay API (MDN)
• Breaking Out of the Box
• Explainer
• Window Controls Overlay Spec