use a more vibrant color for player

- adjust styling of the play button
- adjust text size on library cards

export without library cards
also, add screenshots for review

see issue 1073

- rounded 3-dots button, shorter menu with icons
- group subscribe buttons
- fix artist channel for desktop
- "add new" button to match the current design

with label, constraints, and buttons to replace / remove the picture

- fix missing fields to channel properties
- for channel headers, use same layout on mobile than on dekstop
- add (rough) popovers to channel menu and profile menu
- add wire to edit channel

- place toggle buttons across 2 columns in timer
- less verbose streaming quality options
- keep popup width, decrease font size

- target only single episodes upload for 0.21
- replace "categories" with "season" in podcast details
- add spinners and play buttons to batch upload
- show file extension as tags
- go back to overview after each edition