Snippet: How to add custom blocks to Navigation menus

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Discussed in #355

^{Originally posted by ndiego December 9, 2024}
Adding custom blocks to the Navigation block is a common need, such as blocks for icons or a mega menu. By default, the Navigation block restricts the blocks that can be used within it. However, with a bit of code, you can enable your custom block to be used in Navigation. This snippet will show you how.

This idea originated from this discussion in WP Slack.

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@ndiego mentioned

In preparation for this snippet (hopefully) being approved. I have started an initial draft: https://docs.google.com/document/d/1d9_Emzx-zVQn6YFS6A7xTru500y-oqs6yqa85jjvQQI/edit?tab=t.0

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@ndiego Just finished my first review.