Clarifying some language standards for the docs

Hi everyone!

In a conversation on #3131, we thought it might be helpful to add a few language-related standards. These standards here outline basically what we've done on the past, though we're certainly inconsistent in a few places with the titles at least.

| Q             | A
| ------------- | ---
| Doc fix?      | no
| New docs?     | no
| Applies to    | all versions
| Fixed tickets | n/a

Thanks!