Improve documentation

[BenediktBurger]

Address some issues from #40

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.59%. Comparing base (5235b4d) to head (9ebb869).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #80   +/-   ##
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  Coverage   87.59%   87.59%           
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  Files          36       36           
  Lines        2903     2903           
  Branches      355      355           
=======================================
  Hits         2543     2543           
  Misses        300      300           
  Partials       60       60           

Flag	Coverage Δ
unittests	87.59% <ø> (ø)

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[BenediktBurger]

I added (mermaid) flow charts to the GETTING_STARTED.md to make it easier to understand, how the different components work together.

The diagram information is only additional to the text, so if it does not render, it is only a small part of source code to skip.
The readme links to the GETTING_STARTED.md on github, and github can render mermaid, which should work well.

What do you think, @bilderbuchi , @bklebel ?

[bilderbuchi]

I think it's no problem to add mermaid blocks.

[bklebel]

looks quite nice! :)

[BenediktBurger]

Thanks!