Design and implementation of the Share button everywhere

[mblomdahl]

When I open a video such as this one, https://OwnTube-tv.github.io/web-client/video?id=dbb950a2-b4b6-4387-a1a5-bd3d3815d023&backend=media.privacyinternational.org, I get a very nice pop-up with URL and QR code to share:

I would like to have the same Share button as we have on videos, in the top-right corner of the following views:

1. Site overview page like this one, https://owntube-tv.github.io/web-client/?backend=media.privacyinternational.org, the pop-up should have title "Share video site" with copy-URL and QR code
2. Channel overview page like this one, https://owntube-tv.github.io/web-client/channel?backend=media.privacyinternational.org&channel=podcast, the pop-up should have title "Share video channel" with copy-URL and QR code
3. Channel Category page like this one, https://owntube-tv.github.io/web-client/channel-category?backend=media.privacyinternational.org&channel=podcast&category=14, the pop-up should have title "Share video channel category" with copy-URL and QR code
4. Playlist page (not yet implemented?), the pop-up should have title "Share video playlist" with copy-URL and QR code
5. Channel Playlist page (not yet implemented?), the pop-up should have title "Share video channel playlist" with copy-URL and QR code

(And, logically, the current "start at playback mm:ss" control should only be on individual videos.)