Add codespell configuration, fix a few other typos

[mwtoews]

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This PR adds a configuration for codespell, a tool that has been used a number of times in this project. A few more typos are identified and corrected.

A CI code quality check can be added to use this configuration to run codespell, but I'm not sure how the CI is configured for this project.

[mwtoews]

Suggestions applied, and found a few other typos with a develop version of codespell.