introduce `MessageReactionsModal`. `MessageReactionsModal` shows all the users who have reacted to a message, what their username is and what reaction they used. I decided to punt the implemenation of the filter buttons at the top of the design since every message will be a like for the moment
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Depends on D6301
Linear Task: [[ https://linear.app/comm/issue/ENG-2718/add-reaction-list-modal-on-web | ENG-2718 ]]
[[ https://www.figma.com/file/a1nkbWgbgjRlrOY9LVurTz/Comm-%2F-Desktop-app?node-id=7506%3A140269&t=SceG5J9h4Lt21S30-4 | Figma ]]