Hypercast per Radian LLC

There are significant internal changes to support using special
behavior on specific streaming sites, to allow support for sites that
don't follow modern internet standards for video playback. This works
by letting you configure, for a given site, replacements for the
default "play", "pause", and "go to timestamp" functions that
Hypercast would normally use. The interface is not especially
user-friendly at this stage; you can edit a raw JSON object in the
settings dialog. This will be improved in future, and documentation
added. The default setting enables support for Hulu, which should now
function properly most of the time, instead of not working at all,
which was the previous behavior. Note that this feature does not work
on Chrome due to limitations imposed by Google, which are unlikely to
ever be lifted. Therefore, working sync for Hulu (and other sites you
may configure with special behavior) is only supported on Firefox.
(You get an error message if you try to activate Hypercast on Hulu in
Chrome, rather than the previous behavior of it turning on and
breaking everything.)

The options dialog also has padding on the bottom now, so it looks
less terrible in Firefox.

The message "Content script: waiting for user to click extension icon
in toolbar" is now logged in the browser console. This hopefully makes
it more clear why nothing further happens on page load without manual
user interaction.

When you click the extension icon, an overlay is now displayed with
some basic status about what the extension is doing, which makes it
easier to troubleshoot without having to look at the debug logs. You
can minimize the overlay to an icon and re-expand it by clicking the
minimized icon. The appearance of the overlay is rough and will be
improved in future.

The overlay can now be used to enable and disable syncing. If
something bugs out and you just want to continue watching the video,
you can toggle sync off. This divorces your client from the session in
a reversible fashion, without you needing to refresh the page. Your
updates will not affect other clients, and other clients' updates will
not affect you. You can re-enable sync at any time, which will move
your playback state to match other clients'. When sync is disabled,
another checkbox appears that allows you to enable skew. This is an
advanced feature to work around dumb-as-nails anti-consumer
anti-features present in sites like Hulu, where depending on ad
playback, different people can have different episode runtimes and
different playback positions for the same moment in a TV show. The
usage is as follows: if your playback is out of sync after an ad,
then pause playback, disable sync, manually synchronize your playback
(either you or others can adjust playback position to a known-good
point, like a scene transition), enable skew, re-enable sync. If skew
is enabled when re-enabling sync, your current offset from other
clients' shared playback position will be stored (locally, does not
persist after page refresh) and transparently subtracted out from all
communications with other clients. This means sync works as before,
but with a fixed offset between your playback position and others'.