Added spelling CI

[prestoncarman]

Highlights from CHANGELOG.md

• Added a CI workflow to check for spelling errors

Issues Fixed

• Fixes Add Spell Checker #311

[ianfixes]

I'm embarrassed to see how thoroughly overdue this was. Thank's for adding it.

However, everything under cpp/arduino/avr should be ignored -- these are copied from the Arduino project and it will make diffs really difficult if we make cosmetic changes in there.

The changes to those files should be reverted and the spellchecker should be configured to ignore that directory.

[prestoncarman]

The files under cpp/arduino/avr have been reverted and the configuration for codespell has been update to ignore this directory.

[ianfixes]

Awesum! This wsa soerly nedeed.