Restore "Mark as read"

[fregante]

The feature was dropped in 606d022#diff-ee206f3e88c066917fc8b643bf8fa7a6 because it's incompatible with the new Notifications style and the button itself needs better CSS.

Help wanted to restore this feature.

Moved from #93

[silverwind]

Should add both the "Done" and "Unsubscribe" buttons present on the notifications page.

[fregante]

It appears that if we load the missing script on the page, this will start working without extra JS code.

Missing script: https://github.githubassets.com/assets/notifications-v2-bootstrap-9ab1c3e0.js

We can get this URL from the notifications page and inject it only once the user opens the dropdown.

The second part of this issue would be to restore the buttons via CSS and fix their position/size/spacing (smaller and more compact)

[mallowigi]

I've opened a PR, please take a look.

[tanmayrajani]

This got implemented in #98. Closing.