ci: fix goreleaser/nFMP build for goreleaser 1.21

docs: Release 0.21

Add MPD Outputs dialog (resolves #44)

fix: rpm dependencies (#46)

Overrides goreleaser rpm dependencies and sets them as glibc and gtk3

docs: README: update screenshots

Add missing items to Keyboard shortcuts info window

ci: fix goreleaser screw-up with icon path

ci: Fix Go version at 1.14.7 to address snap build errors

Fix possible race in schedulePlayerSettingChange

Select top item in Streams by default