Put all illustrations in our picture slide deck

[lscheske]

We spend quite some time making slide-decks (Google Slides, Keynote, Powerpoint), and they don't support inserting SVG files.

Could we have all the illustrations added to this slide-deck, for ease of access?

This should be updated with all new illustrations as they are developed.

[fdeerenberg]

I have put the old illustrations in because the restyling is not finished yet.

[ElenaFdR]

I'll close this issue after the slide deck has been linked from the illustrations repo and About.