Pull Requests Counter by Martin Cavoj

With this extensions, you can immediately see whether you have any pull requests assigned to you on Github. If there are none, the badge is green, if there are less than 3, it is yellow, otherwise it's red. This pushes you to do the code reviews as soon as possible.

Clicking on the icon brings you to the Github page, where you can see the assigned pull requests.

The only thing which needs to be configured is the Github API token. Just follow the instructions on the options page of the add-on.