Correct inconsistencies and errors in Nav Editor docs

[getdave]

Description

Following as discussion with @talldan I discovered that there are some inconsistencies in the Nav Editor docs. This PR corrects these. See individual commits for specifics.

How has this been tested?

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]

Thanks for noticing this and updating it 🙇

[getdave]

Thanks for noticing this and updating it 🙇

@talldan Just noticed your 👍 here. I made some additional changes. Are you still happy?

[getdave]

I haven't forgotten about this...

[Mamaduka]

The update looks great, Dave.

The "Hooks" section is updated, but I can correct it in follow-up PR today/tomorrow.

The new central hooks are useNavigationEditor and useNavigationBlockEditor. The Layout component itself had many changes and probably won't fit in the small snippet we currently have in docs.

[getdave]

Seeking final ✅ on the basis that the scope of this PR is to

• correct inconsistencies
• correct errors

🙏 😄

[Mamaduka]

I think this PR is in good shape, and all feedback got addressed 🌟

I'll do a follow-up for hooks tomorrow.