Turn examples into crates

[stefan-k]

Closes #307

• Port all examples
• Adapt all examples links in docs
• adapt docs

notes

• wasm32-unknown-emscripten build fails on new examples because "emcc" cannot be found. This is why examples are now excluded from that build. To make this easier, examples are named "example-".
• Also wasm32-unknown-unknown fails when intel-mkl is involved. I have deactivated the examples in the wasm CI builds.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (26c7d68) 90.16% compared to head (ed489c8) 90.25%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #387      +/-   ##
==========================================
+ Coverage   90.16%   90.25%   +0.08%     
==========================================
  Files         141      141              
  Lines       19679    19679              
==========================================
+ Hits        17744    17761      +17     
+ Misses       1935     1918      -17     

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