Optimize PNG resources

[Pyker]

We should run our PNG resources through something like optipng or TinyPNG, to save up on resources.

[github-actions]

This issue is stale because it has been open for 90 days with no activity.

Easy win would be to install Imgbot app https://github.com/marketplace/imgbot

[Pyker]

Thanks for your input, but this is a simple task and I don't think a GH app is necessary for this.