Adds assignee for issues which are marked to be "Fixed" by a pull request, and adds the "In Progress" label.
For users who would be affected by an issue (including the issue's creator), it is useful to receive progress updates once efforts have begun to address the issue.
Issue assignment is a useful GitHub feature for developers, as it can avoid a scenario where multiple developers spend effort toward resolving the same issue due to the fact that progress was not clearly communicated.