Update icon themes
We have currentlyMaintainer: Andreas Kainz
- breeze, breeze_dark
- elementary, elementary_svg
- colibre, colibre_svg
- sifr, sifr_dark, sifr_svg
- tango, tango_svg
The default icon theme takes a) Hicontrast if the system is configured accordingly, b) the system theme if matching one of the shipped, or c) Breeze on KDE and macOS (not on the macOS appstore; with the dark variant if the system theme is dark), Elementary on Gnome (changed for 6.1 with tdf#116695), and Colibre for everything else (fallback).
-> Suggested in tdf#75398 is a switch from Hicontrast to Sifr (agreement from Hypra requested).
-> As Breeze is not shipped on the macOS app store we better go with Colibre (Sifr was refused, tdf#116693)
When an icon theme misses an icon we have a fall back strategy with sifr_dark -> breeze_dark or sifr, breeze_dark -> breeze or industrial, tango, breeze -> galaxy (and finally just the label is shown if galaxy and helpimg fail, e.g. TSCP toolbar)
-> Plan is to fall back on Colibre if it's complete (tdf#116696)
-> Move Industrial, Tango, Galaxy, Oxygen, and Hicontrast into extensions (tbd)
Unrelated but relevant is the effort to use SVG icons (tdf#115439, WIP by Tomaz)