Improve make.jl

[kellertuer]

The Documentation now automatically detects whether the tutorials are present (or will be rendered).
In case they are not present and will not be rendered in this run, they are excluded automatically from the menu.

This resolves #423.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.90%. Comparing base (9e185a8) to head (b2fd86e).
Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #424   +/-   ##
=======================================
  Coverage   99.90%   99.90%           
=======================================
  Files          78       78           
  Lines        8289     8289           
=======================================
  Hits         8281     8281           
  Misses          8        8           

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🚨 Try these New Features:

• Flaky Tests Detection - Detect and resolve failed and flaky tests