Update docs to reflect new automated process for feature grouping

[getdave]

Description

In #33229 we added automation to the release tooling to attempt to auto-categorize the grouping of PRs by "feature".

This PR updates the docs to reflect that and to add information on exactly how you should look to curate the changelog in response to what the script will output.

How has this been tested?

Reading and checking for accuracy.

Screenshots

Types of changes

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• I've tested my changes with keyboard and screen readers.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR (please manually search all *.native.js files for terms that need renaming or removal).

[talldan]

Looks good. The only other thing I did was to ping a few folks who'd worked on, reviewed or merged an uncategorized PR to let them know why the labels are important.

It'd be good to have an automated task do this, but in the meantime it could also be worth mentioning in the docs.

[gziolo]

The only other thing I did was to ping a few folks who'd worked on, reviewed or merged an uncategorized PR to let them know why the labels are important.

Could we add a logic to Pull request automation workflow that fails the check if there are no labels? Ideally, one of them should be prefixed with [Type] and the other one should map to one of the feature groups.