Better fullscreen + dock player mode

[4www]

• improve fullscreen mode by using the browser's fullscreen. It allows us to have on mobile and desktop a better experience since the browser's URL bar is hidden, and only the radio4000-player (Aside--right, to have the r4-cms layout controls) is displayed fullscreen.
• add a new mode, docked, at /channel/player.
  It shows the channel cover image in fullscreen, a play button, then the player displayed in the DOM (static, docked). The UX should favor movements between modes.

[oskarrough]

The docked mode looks pretty with the background. Also great having proper fullscreen.

When you tap the button to dock the player, I'm not sure how to exit it again. If you click the same button again, it moves player to the "sidebar-mode" but stays docked? Only way is to use the browser's back button or the menu? Maybe this is ok.

When in fullscreen, and you tap "docked", you end up in a mode without background. Hide "docked" button when in fullscreen?

[oskarrough]

when in docked, I can tap left and right to go back. neat! can we also have it work on top and below?

[oskarrough]

more blur? 1px makes it seem like it's just a bad quality image.

[oskarrough]

could also load a bigger image here, if we want?

[oskarrough]

When you land on https://deploy-preview-394--radio4000.netlify.com/radio-island-breeze/player, it shows a button instead of the player. Why not have the player immediately?

[oskarrough]

When I tap "escape" in fullscreen, I get this error:

radio4000-2a1de9342cad2f9255eb1720d34cb05f.js:466 Uncaught (in promise) TypeError: Document not active
    at n.exitFullscreen (radio4000-2a1de9342cad2f9255eb1720d34cb05f.js:466)
    at n.toggleNormalFormat (radio4000-2a1de9342cad2f9255eb1720d34cb05f.js:466)
    at n.toggleDockedFormat (radio4000-2a1de9342cad2f9255eb1720d34cb05f.js:466)
    at n.toggleDockedFormat (radio4000-2a1de9342cad2f9255eb1720d34cb05f.js:289)
    at n.send (vendor-b5275e113e0b5e284eb9f99b7b50fc55.js:2985)