Allow notifications to have links

Sometimes a notification leads to another page, so it makes sense allowing to click on it to see more info

~Although clicking by default closes that notification IIRC, so may be confusing, so we have to remove that first~

In fact we can just make so that the notifications can receive an arbitrary JSX element as opposed to just a string as it's currently implemented.

Locate the notification implementation and inspect how its current string-only message is rendered and dismissed. Done when notifications can receive an arbitrary JSX element, including a link, and the click behavior is clear rather than unexpectedly closing the notification.

Written by the indexing model from the issue text.