use Modal Images for controller images

[ellensp]

Add Model images to https://marlinfw.org/docs/hardware/controllers.html

Firstly for the record, I'm not a web developer, I only found out that Model images was a thing today while looking at bootstrap. Basically I followed https://www.w3schools.com/howto/howto_css_modal_images.asp and https://stackoverflow.com/questions/47798971/several-modal-images-on-page

The current way to view the high resolution images opened up a new browser window. This is rather primitive.
With Modal Images it opens up over the top of the webpage with a close gadget, this is much more intuitive.

As a benefit of using Modal Images the *_thumb.jpg files are no longer required and are generated as needed.

I'm not sure of the best places to add the css and javascript when it comes to jekyll so feel free to move things about.