Add codespell

[guarin]

We should add https://github.com/codespell-project/codespell to check spelling in our source code and docs.

TODO

• Add codespell dev dependency to pyproject.toml
• Add codespell rule to Makefile
• Check how many errors we get. Fix errors if there are just a few of them. Otherwise skip all files with errors and then fix files one by one in follow-up PRs.