AvatarStack doesn't allow non-avatar elements in the stack

[t3chguy]

Element Web's FacePile looks like this:

It has an extra overflow tile "..." at the end which follows the stacking behaviour. Due to the styling of compound-web the style is not applied and it ends up not being stacked.

Either relax the selector or export the class/wrapper element to allow stacking things other than Compound avatars to enable wider reuse. Otherwise code ends up having to work around it and duplicate logic which can de-sync:

Partly caused element-hq/element-web#26112

[Johennes]

Once this is done, we should also clean up the temporary workaround made in matrix-org/matrix-react-sdk#11527.

[t3chguy]

This was fixed by @germain-gg