[FEATURE REQUEST] - Prose linting

[hey-august]

Is your feature request related to a problem? Please describe.
Yes. Our development (authoring) and CI/CD pipelines don't enforce most of our style guide, or even grammar/spelling rules.

Describe the solution you'd like
Integrate Vale:

• Install as CLI tool
• Configure linting to enforce our Style Guide and best practices
• Consider adding to start command to warn about issues while authoring
• Consider adding to build checks via existing Github Action, or otherwise adding to build process

Describe alternatives you've considered
Vale is the most popular tool for this purpose.
Other options include:

• remark-lint: I think this is probably the main alternative we should look into, since it's a plugin in the Remark ecosystem that we already use.
• markdownlint
• proselint
• write-good: More general-purpose, would likely require more setup

Additional context
Article: Style guides, linters, and Vale: Why do tech writers need this?

Also consider precommit