Themes should distinguish between selections, cursors and anchors/head

[lucmos]

Hello, thank you so much for the awesome work!
I was trying to decide on a theme, and noticed that not all themes offer the same amount of information.

For example, compare the gruvbox dark (whose I am a fan of) and the catppuccin theme:

• (first row) In gruvbox there is no information about the secondary head (cursor) positions (A-; visually changes only the primary selection).
• (second row) In gruvbox it is difficult to distinguish secondary selections from the background

Gruvbox	Catppuccin