[WIP] Menu at right side & collapsible

[wilzbach]

As said on #52, hacking this together seems doable. However this is far from complete, but I thought I open it as PR, s.t. giving feedback is easier & everyone can easily checkout this PR and continue the work or give feedback.

To-do

• test with IE

Discuss

• next/prev buttons
  • top / bottom ?
• get feedback about a fixed code box width: currently the text and code box use 50% each, should we keep this or use a smaller width for the code box (we could fix the code box to X pixels and then let only the text box expand)
• get feedback whether we should display the examples in the text box (for example like here: http://rustbyexample.com/generics/phantom.html)

Please feel free to extend this list or add comments ;-)

Done

• menu on the left
• collapsible menu categories
• toggleable menu for mobile
• fixed height for text and code box (as discussed in make text and code box fixed height and allow scrolling #54)
• Use entire width if no code is provided
• toggle-able menu for the desktop
• clearer/thinner menu styles
• CSS highlight styles for the current page
• Fix 99vh hack for the menu bar height (needed to avoid a page scrollbar)

How it currently looks

Desktop:

Mobile:

[PetarKirov]

Ping, I would love to see this merged! Unfortunately I don't have time to review the implementation right now.