Add missing image

[kikoso]

The image from the main README is missing.

It could alternatively be removed from the README itself, this PR just restores it on the docs folder.

[codecov]

Codecov Report

Merging #4834 (f1d7778) into main (0a5b843) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##               main    #4834   +/-   ##
=========================================
  Coverage     84.75%   84.75%           
  Complexity     3431     3431           
=========================================
  Files           491      491           
  Lines         11278    11278           
  Branches       2076     2076           
=========================================
  Hits           9559     9559           
  Misses          673      673           
  Partials       1046     1046           

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