Review screenshots in docs

[hturner]

In v0.3 we added a workflow to optimize screenshots using an R script. In some cases the optimization was too harsh, leading to screenshots that are blurry. Some updates were made to the R script to improve the optimization, but in some cases we still have a blurry version.

So, we now need to

• Review the screen shots in the documentation and identify ones that are blurry (or otherwise need updating)
• Retrieve the originals from the git history or take new screenshots
• Run the optimize R script on these screenshots and check the results. Modify the R script again if required (e.g. can the optimization be skipped for screenshots that are already <100kb?)
• Commit the updates to a branch of the R Dev repo and make a PR to the devel branch