Make docs work better on mobile

[fhennig]

As a user of stackable I'd like to read the docs on mobile too, to maybe check up something while on the go.

As a potential customer it'd be good to have working docs should I check on stackable while on the go.

This is done when:

• The hamburger menu is fully in frame and the menu is usable easily
• The content pages render for mobile and not in full desktop view, requiring me to scroll out a lot

This is what it looks like on my iPhone 10 with Safari (not sure what version it is)

On this page, the page does not scale down. Possibly because of the images?