Add compress image job and fix for unused images function

Adds the image compression task to be run in CI, as well as a version to be used locally. MRs should be created if there are changes and assigned to the user.

Related to #8 (closed)

Testing

Works locally.

In CI, the job worked, and successfully created branch such as compress-images-20241023222637 in internal-handbook with 20 changes commit (branch has been manually deleted).