Add a dialog showing all reactions to a message

[chillmastonmuutos]

This PR partly implements the features described here: https://github.com/vector-im/element-web/issues/9723

What is NOT implemented as in the above issue:

• Timestamps on hover
• Moderator functionalities

Here's a few screenshots:

NOTE! I could not do the sign-off part for this PR, because I do not wish to associate my real name with this GitHub account. I've sent an email to [email protected] regarding anonymous contributions, but so far I've recieved no reply. I'm opening this PR in order to avoid my work going to waste.

---

Here's what your changelog entry will look like:

✨ Features

• Add a dialog showing all reactions to a message (#8051). Contributed by @chillmastonmuutos.

[chillmastonmuutos]

Tests added

[turt2live]

@chillmastonmuutos when you get a chance, can you update this PR to latest develop for us?

[turt2live]

Hi @chillmastonmuutos - our legal department says while they have received your DCO signoff request, they do not have it marked completed.

Until that is completed we won't be able to accept this change, sorry. If you have questions, please forward them to the legal team using the same address you sent the DCO request to.

[hanthor]

Can this be resurrected somehow?

[t3chguy]

@hanthor needs a designer to take it on

[t3chguy]

Thanks for your contribution. I'm going to close this for now as the changes requested haven't been made. If you're interested in continuing to work on this please let us know and we can reopen the pull request. Thanks!

[joerglohrer]

Please reopen this, as it's still not resolved and strongly needed!