Automated spellcheck via GitHub Actions

[SeanKilleen]

I've made this change for a few repositories recently (NUnit, Marten, HotChocolate, Uno Platform, Playwright, etc.). I was going through my starred repositories, and you're a phenomenal leader in the community, so I figured you might benefit from this too.

• Adds GitHub action to run cSpell
• Adds a cSpell configuration file
• Addresses the errors the cSpell finds.
  • In most cases that means adding terms to the dictionary or adding back-ticks around terms that aren't necessarily meant to be words.

I figured it might be valuable especially as you consider additional contributions. If not, I won't be offended if you close it. :)

[SeanKilleen]

Closing since there's been no response. 👍