Fix typos

[hectormz]

This PR fixes some typos found in the codebase/documentation.

Typos were found via codespell and reviewed by a human, so hopefully the changes are appropriate!

[mwouts]

Thank you @hectormz for this. I will give a look soon (I'll have to make sure that the correction on the sample ipynb files were reported as well on the code / markdown representations).

Also, did you include the documentation in the spell check?

[hectormz]

Hi @mwouts ! I'm sorry to put the burden of checking on you. It did run on the documentation, but only found a few clear typos.

Theoretically, the same typos were found in fixed in all the file formats, but it was a little harder for me to diff the .ipynb to check (hence jupytext)

[mwouts]

Thanks @hectormz! I see that all the test ran OK, so indeed the changes on the ipynb files and on their text representation are in line, we're good to go! Thanks again