feat: Add option to disable editors

[rhystmills]

What does this change?

This adds support for a disabled prop to the RichTextEditor.

If the editor is disabled, it's styled differently, the editor content can't be changed, and the menu and keyboard shortcut plugins won't be initialised. The field will instead appear as uneditable text, showing a not-allowed cursor on hover.

This is useful in our apps, where a field will often be disabled if a user lacks edit permissions (for example in tagmanager).

The PR adds some styling hints that the field is disabled, which weren't there in the Scribe editor this replaces.

Disabled Scribe editor:

Disabled prosemirror-editor (not-allowed cursor state not visible):

Enabled prosemirror-editor:

How to test

This has been tested locally in tagmanager. If you wish to do the same:

1. Publish this package locally using yarn yalc from the root of the project
2. Use this branch of tagmanager locally.
3. Add this package to tagmanager using yalc add @guardian/prosemirror-editor
4. Run tagmanager with ./scripts/setup then ./scripts/start
5. Ensure you have tag edit permissions in https://permissions.code.dev-gutools.co.uk/
6. Wait a minute for them to apply. Then, In tagmanager, click an existing tag in the home page and try editing the text.
7. Reverse your permissions in https://permissions.code.dev-gutools.co.uk/ and try editing the tag in Tagmanager again. Does the disabled field act as expected?

[changeset-bot]

🦋 Changeset detected

Latest commit: bdbe9bb

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@guardian/prosemirror-editor	Minor

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[samanthagottlieb]

Just to clarify I understand the release process, it looks from the documentation that this file gets generated automatically by running yarn changeset. Then the changesets GitHub Action will automatically open a release PR which I assume will convert the changeset info into a changelog? (example here)

[rhystmills]

Yes - I was prompted to run yarn changeset by Changeset Bot after my first commit, changesets said there wasn't a 'changeset' and this added one, which I added in a follow-up commit.

[samanthagottlieb]

Have tested locally, revoking and re-granting myself Tagmanager CODE permission - looks good!