treewide: more UX-friendly colors for notification borders

[MrSom3body]

I assert that this feature request is relevant for Stylix

• [x] I assert that this is not a duplicate of an existing feature request.

Description

I’d like to propose changing the color schemes used for notification borders and progress bars across several modules (dunst, fnott, mako, swaync) to better reflect the importance (urgency) of notifications.

I would change the following colors:

• low priority from base0B to base03
• normal priority from base0E to base0D (this actually is written in the style guide but is not used)

I also have a PR ready if these changes would be fine

Notify maintainers

@danth @trueNAHO

[0xda157]

Github seems to have a spam problem right now, I'll unlock this issue in a hour or two