Tabs: Tone down borders
The current tabs are very border-heavy, so they have a strong "inverted" look in dark:
Experiment for reducing the prominence of the borders (within the technical constraints, in an ideal world we'd be able to do something more like this :P):
Main differences:
- No vertical borders on the currently active tab
- Active tab has the same color as raised buttons
- vertical borders between other tabs are not full height
- Maybe also worth considering: Less opaque color for the vertical dividers
cc @aday
Part of #301 (closed)
Edited by Tobias Bernard