Add Imprint

[Pokerkoffer]

This PR adds a optional imprint at the bottom (below copyright) of the email.

[codecov-io]

Codecov Report

Merging #73 into master will increase coverage by 0.13%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #73      +/-   ##
==========================================
+ Coverage   97.81%   97.94%   +0.13%     
==========================================
  Files           3        3              
  Lines        1053     1073      +20     
==========================================
+ Hits         1030     1051      +21     
+ Misses         16       15       -1     
  Partials        7        7              

Impacted Files	Coverage Δ
hermes.go	65.00% <ø> (-3.19%)	⬇️
default.go	100.00% <100.00%> (ø)
flat.go	99.80% <100.00%> (+0.20%)	⬆️

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