Show all reactions in modal

[nadonomy]

(Internal) Zeplin link: https://zpl.io/a3e7okQ

• Accessed from a button labelled 'Reactions' in the more/context menu, which should be absent if a message has no reactions
• Shows timestamp on hover
• Allows moderators to remove reactions, using a vertical [...] & context menu to prevent accidental clicks like the room list

Before kicking off dev, we should discuss:

• Sort orders of reactions (by count?) and names (alphabetically?)
• Confirm we're happy with the design— left panel vertically scrolls if there's too many reactions
• Discuss if we should expose mxid's
• Discuss utility of viewing member profiles from this modal—would need to dismiss the modal to reveal in right panel, which won't feel great

[babolivier]

This would be really helpful. A few orgs using Matrix seem to use the "react here to get an invite/register interest/etc" and it's a bit sad that the only way for them to see the full list of reactions is by looking at a different app (since the Element mobile apps support this use case).