* also apply live-preview if an unsaved style was disabled
* use box-shadow instead of outline for focus everywhere
* allow focus outline on click in text/search input or textarea
* search inputs should use the same style as text inputs
* also use box-shadow focus on delete buttons
* remove URLSearchParams workaround, not needed since Chrome 55
* use `once` in addEventListener, available since Chrome 55
* update USO bug workarounds, remove obsolete ones
* ping/pong to fix openURL with `message` in FF
* use unprefixed CSS filter, available since Chrome 53
* use unprefixed CSS user-select, available since Chrome 54
* focus tweaks
* also use text query in inline search for Stylus category
* use event.key, available since Chrome 51
Co-authored-by: narcolepticinsomniac
* installation URL is preferred - same behavior as before
* @updateURL is used when the style was drag'n'dropped into the manage page
because there's no real URL in this case
* install-usercss page shows the new update URL, which is set as per the above,
under the checkbox that enables updates
@tophf The bold font and copious padding on the install button is overkill IMO. Almost all our buttons are default, but if we wanna go a little bigger, I'd prefer them more like the "overwrite" and "append" buttons.
