Add codespell support (config, workflow to detect/not fix) and make it fix few typos

[yarikoptic]

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.

My attention to this repo brought by an inquiry from @bendichter on behalf of the @dandi project.