[a11y] 9.2.4.3 Conclusive sequence for keyboard operation

[tschiebel]

audit: https://infinite.owncloud.com/s/PnaAukHGGsLnrMM

https://bitvtest.de/pruefschritt/bitv-20-web/bitv-20-web-9-2-4-3-schluessige-reihenfolge-bei-der-tastaturbedienung

Personal

• If you open and exit menus or user-defined tooltips with the keyboard
  they remain open. This means that visually hidden elements often retain
  many cases receive the keyboard focus. To avoid this, the elements should
  elements are best closed automatically when they are exited.
  are left.
  

• In the mobile view, when the "Details" area (e.g. "Shares") is open,
  visually hidden elements in the background can be accessed by swiping backwards with the
  the keyboard. This should be avoided.
  

Shares, Spaces

• See comments on Personal