Link KQCircuits-Examples to docs

[nikosavola]

Notebooks in KQCircuits-Examples could be included to the documentation with nbsphinx or MyST.

Duplicate of iqm-finland/KQCircuits-Examples#3

[nikosavola]

I made an example in main...35-nbsphinx-kqc-examples which works, but it isn't very nice to git clone every time make html is performed. Should we instead do an optional git submodule, such that the docs could compile without warnings without the repo as well.