Turn examples into crates

[stefan-k]

Closes #307

• [x] Port all examples
• [x] Adapt all examples links in docs
• [x] 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 :white_check_mark:

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

Additional details and impacted files

```diff @@ 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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