add app icon

[hurradieweltgehtunter]

In addition to the new app images the icons get updated, too.
@mmattel @pmaier1

Fixes #31

[codecov]

Codecov Report

Merging #61 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master      #61   +/-   ##
=========================================
  Coverage     69.46%   69.46%           
  Complexity       37       37           
=========================================
  Files            11       11           
  Lines           167      167           
=========================================
  Hits            116      116           
  Misses           51       51

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[mmattel]

@karakayasemi @pmaier1 mind to approve ?
(to view the image you can use: https://codepen.io/LeftyDesigner/pen/gLabt and c/p the content into)

[karakayasemi]

@mmattel thank you for reminding me.