Improve the manual for screen reader users (screenshots)

I heard from @donuts that the manual is getting an overhaul. It would be great if, as part of this, the manual could be written in a way that works for low vision and/or screen reader users.

As mentioned in #132 there are parts of the manual that rely on the user being able to visual process a screenshot. This does not provide assistance to users who cannot do so (easily).

Whilst good alt text may alleviate this, alt text is not necessarily easy for a user to step through, or interact with (copy and paste, etc). Therefore, it would be great if the text could be written so it works without any screenshots, and just add the screenshots as an additional visual aid.

/cc @championquizzer @gus