Add Mobile layout

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Depends: #504
Closes: #64

Todo:

• Add Waitlist and User list somewhere
• Add stripped-down PlaylistManager for showing individual playlists
• Fix some of the weird margins in SettingsManager
• Add small style for media items in RoomHistory, perhaps not showing votes unless item is selected
• Show vote icons on top of video after a tap
• Full-screen dialogs if in mobile layout
• Probably more

[pledi]

I think combining both waitlist and userlist might be good for mobile.

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Note to self: all mobile specific css can go in mobile/ and have the relevant media query applied automatically using

@import "./mobile" (max-width: 768px);

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Should lock the screen orientation to Landscape when fullscreen video is enabled:

https://developer.mozilla.org/en-US/docs/Web/API/CSS_Object_Model/Managing_screen_orientation
https://w3c.github.io/screen-orientation/#locking-the-screen-orientation

e; And also probably use this mobile layout in portrait mode only.

[goto-bus-stop]

Will wait for material-ui@1.0.0 before really continuing with this, I think. 1.0.0 will include better mobile support eg. for Dialogs so it'd be a waste to implement it here and then move it over once 1.0.0 is out.

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Hmm a volume control would be nice, since it defaults to 0% 😂

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SoundCloud player on mobile can't autoplay, so we should show the audio element on the first SC track or something so users can allow it to play.

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This is incomplete but rebasing all the time is a pain, so I'll merge it now and work on remaining issues later. I added a warning about it being crashy and in beta that shows up when you enter the mobile layout.