meta: Reduce repo to Core and Development apps
Part of GNOME/Initiatives#35
At least the following apps don't seem to be GNOME Core apps. Would it be possible to move those and potentially others to other-app-mockups to avoid confusion?
- contrast
- crosswords
- endeavour
- fractal
- inkscape
- metronome
- notes
- reading-list
- secrets
- social
- sound-recorder
- tetravex
- tilix
- tweaks