/api/live/create: Include new thread ID in JSON response.
Move websocket URL to /live/{event}/about.json.

This allows API clients to get the URL and use it.
Document the API.
OAuth: Add scopes to some endpoints

Adds "read" scope to GET_listing
Adds "submit" scope to POST_update
Adds "edit" scope to striking/deleting updates
OAuth: Add scopes to the rest of the API endpoints.
Store description on POST_create.
Allow a subreddit's styles to be used for embedded threads.

Adding ?stylesr={srname} to the /live/whatever/embed endpoint adds that
subreddit's stylesheet to the embed.  This allows for custom theming of
embedded live threads.
Add high-selectivity margin setting for .content.

Subreddit stylesheets commonly add an extra margin at the top of
.content to allow room for an announcement link or the like. By
increasing the selectivity this way, we override the common case without
making it impossible to override if it's really desired.
Overhaul the on-reddit embed to look more natural.

This does a few things:

* takes advantage of the new unsandboxed version of mediaembeds from
  r2 to remove one unnecessary level of <iframe>s.
* styles the embed to look more like a regular old self post.
* applies the current subreddit's stylesheet to the embed to allow
  the embed to be in-theme for a subreddit.
Use media_domain for embed URL.
Guard against pref_show_stylesheets being bad in UnloggedUser case.
Fix qproc usage of media embed.
Ensmallen the headline and status bar.

(It's totally a cromulent word.)
Add hr and blockquote style.
Fix wrapping for sidebar and contributors.
Mobile: get rid of extraneous whitespace when no #liveupdate-options.
Get rid of the welcome bar on all liveupdate pages.
Fix liveupdate logo replacing <h1> in login popup.
Split the description sidebar into description and resources.

The (low length limit) description field will be useful for embeds and
for summarizing the thread. Resources will become collapsable
eventually.
Add OpenGraph data to the live pages.