Add support to mark videos as spoilers (#2255)

* Add support for MSC4193: Spoilers on Media

* Clarify variable names and wording

* Restore list atom

* Improve spoilered image UX with autoload off

* Use `aria-pressed` to indicate attachment spoiler state

* Improve spoiler button tooltip wording, keep reveal button from conflicting with load errors

* Make it possible to mark videos as spoilers

* Allow videos to be marked as spoilers when uploaded

* Apply requested changes

* Show a loading spinner on spoiled media when unblurred

---------

Co-authored-by: Ajay Bura <32841439+ajbura@users.noreply.github.com>

src/app/components/message/content/ImageContent.tsx

@@ -214,7 +214,7 @@ export const ImageContent = as<'div', ImageContentProps>(
         )}
         {(srcState.status === AsyncStatus.Loading || srcState.status === AsyncStatus.Success) &&
           !load &&
-          !markedAsSpoiler && (
+          !blurred && (
             <Box className={css.AbsoluteContainer} alignItems="Center" justifyContent="Center">
               <Spinner variant="Secondary" />
             </Box>