[Website] Example image broken, images too large

[sbryngelson]

https://mflowcode.github.io/documentation/md_examples.html

The image for 'linear theory' for 3D Rayleigh-Taylor and body forces cases @wilfonba is broken somehow. It points to https://mflowcode.github.io/documentation/linear_theory.jpg

Also, the images on this page are quite large, making it hard to scroll through. Making them smaller would be useful.