Fix typos discovered by codespell

[cclauss]

% codespell --ignore-words-list=crate,fo,ser --write-changes

• https://github.com/codespell-project/codespell/blob/master/README.rst

[casey]

Very nice!

[cclauss]

It is unfortunate to put the misspelling in the commit message like:

Fix typo: argumant -> argument (#1257)
Fix readme typo: interpetation -> interpretation (#578)
Fix typo: chracter -> character (#561)

because then it is difficult to find that misspelling again with automated tools.

[casey]

Yah, agreed. Definitely my fault, I usually write the commit messages. And we can't really run codespell as an action on the commit messages, since I usually write them from the interface on github.com in the squash-and-merge button.