Add codespell support (config, workflow to detect/not fix)

[yarikoptic]

Got here as a "heavy" "user" of git-annex which uses this library . Thank you for developing it!
While checking out

• S3 support GET versioning #290

decided to check if I could contribute ;) @joeyh could attest that I am generally a sane person and not a bot.

More about codespell: https://github.com/codespell-project/codespell .

I personally introduced it to dozens if not hundreds of projects already and so far only positive feedback.

CI workflow has 'permissions' set only to 'read' so also should be safe.

[joeyh]

FWIW, I have cherry-picked the two commits that fix spelling issues.

As far as the github actions stuff goes, I avoid using github to that extent (use is limited to typing in text boxes like this one and occasionally pushing to other people's repos), so don't feel qualified to deal with it.

[yarikoptic]

FWIW - rebased the branch so it reflects that typo fixes were applied. reconfirmed that no new added (well -- I also added to skip re-used). note that github ci is read-only and is just to detect so not much "handling" of it is needed.