admin UI

I was informed that the current warning if you @ a remote server in a private post is inadequate. These are suggested changes to better inform users.

Descriptions of differences between scope are more clear

add ability to open status by URL from search (fix #53)

"Various apps are available" is now a hyperlink

adjusted to allow choosing it, yet

some weird mobile browser behaviours

Technically the check for iOS from components is a side effect, because it's
neither in state nor props, but the user agent does not change, so I think
that's okay.

before. In the API, attachments now can be either image, video or gifv. Gifv
is to be treated like images in terms of behaviour, but are videos by file
type.

Remove note about following Gargron@mastodon.social from getting started text

loaded status; do not preload submitted statuses into community/public
timelines, unless those timelines have already been loaded; do not
close streaming API connections for community/public timelines, once
they have been established (most users navigate back to them eventually)

for those errors