Cover/Accordion: Exit on Enter

[ocean90]

What?

Closes #77294.

This PR adds the __experimentalOnEnter support key like done in 223baa2 and already used by other blocks: https://github.com/search?q=repo%3AWordPress%2Fgutenberg+__experimentalOnEnter+language%3AJSON&type=code&l=JSON

Why?

It solves the problem of not be able to exit the block by pressing enter, it only adds empty paragraphs.

How?

Adding __experimentalOnEnter to supports config in block.json.

Testing Instructions

1. Add a Cover block
2. Select a color and enter some text for the first paragraph
3. Click enter twice

Testing Instructions for Keyboard

Screenshots or screencast

Bildschirmaufnahme.2026-04-14.um.11.08.53.mov

Use of AI Tools

None.

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