Docs: Copy and formatting edits for the "Registration of a block" guide

[ndiego]

This PR focused on formatting and copy edits for the Registration of a block guide. The goal is to fix a few formatting issues and improve readability.

[github-actions]

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Props ndiego, greenshady.

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Co-authored-by: ndiego <[email protected]>
Co-authored-by: justintadlock <[email protected]>

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[github-actions]

Flaky tests detected in 8b78576.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/7794193216
📝 Reported issues:

• [Flaky Test] name is correctly hydrated for different values #57881 in /test/e2e/specs/interactivity/directive-bind.spec.ts