Add feedback mechanism for beta features, namely Spaces

[t3chguy]

Fixes element-hq/element-web#17238

[niquewoodhouse]

@nadonomy I just want to justify my overkill with the feedback button in these designs!

• Same component keeps it simple to edit/remove/maintain
• Being overly loud with it for the first release will hopefully lead to more early feedback > hopefully improve early versions
• Can be removed/amended later when we have more of a handle on feedback
• Being overly loud with it will give non-technical users more of a chance to feedback, where they currently have none.

I had a bunch of other suggestions but they're not feasible in time for the next RC/need more time.

[jryans]

Looks great to me code wise, thanks! 😄

[nadonomy]

@nadonomy I just want to justify my overkill with the feedback button in these designs!

@niquewoodhouse consider the overkill justified! I think the consistency of execution makes it really easy to develop blindness to them if you want to. Plus, we can always remove them in future if they turn out to be too much. Thanks for actioning quickly!