Use codespell in CI to spot spelling errors

[simonw]

I noticed Rich is using this: Textualize/rich@9c12a45#diff-ce84a1b2c9eb4ab3ea22f610cad7111cb9a2f66365c3b24679901376a2a73ab2

Ran it against the Datasette docs and found a bunch of obvious fixes, surprisingly with no false positives.

datasette % codespell docs/*.rst
docs/authentication.rst:63: perfom ==> perform
docs/authentication.rst:76: perfom ==> perform
docs/changelog.rst:429: repsonse ==> response
docs/changelog.rst:503: permissons ==> permissions
docs/changelog.rst:717: compatibilty ==> compatibility
docs/changelog.rst:1172: browseable ==> browsable
docs/deploying.rst:191: similiar ==> similar
docs/internals.rst:434: Respons ==> Response, respond
docs/internals.rst:440: Respons ==> Response, respond
docs/internals.rst:717: tha ==> than, that, the
docs/performance.rst:42: databse ==> database
docs/plugin_hooks.rst:667: utilites ==> utilities
docs/publish.rst:168: countainer ==> container
docs/settings.rst:352: inalid ==> invalid
docs/sql_queries.rst:406: preceeded ==> preceded, proceeded

[simonw]

Docs: https://pypi.org/project/codespell/

There's a codespell --ignore-words=FILE option for ignoring words. I don't have any that need ignoring yet but I'm going to add that file anyway, that way I can have codespell be a failing test but still provide a way to work around it if it incorrectly flags a correct word.