Follow users from notification that new user signed up on local instance

Clear and concise description of the problem

As a user, when a new user joins my local instance, I want to be able to follow them from the notification that they have joined.

Suggested solution

Put the follow/unfollow widget on signup notifications. Additionally, make the username as well as the display name accessible somehow.

Alternative

I have to go back to the default interface, scroll to the right place in my notifications, and follow there.

Because only the display name, and not the actual username, is displayed, I can't even type in the user's handle in the explore tab to follow them; there simply isn't enough information to take any action from within Elk.

Additional context

I have tried tapping with all the mouse buttons and hovering, and on mobile long-pressing, and have not been able to generate any interaction with the highlighted user name.

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