Feature : Inserter Priority for Custom Blocks

[Vrishabhsk]

What?

• Closes Allow custom blocks to influence display order in Inserter #73915
• Adds support for inserterPriority property in block.json, allowing custom blocks to influence their display order in the Block Inserter.

Why?

Currently, block developers have no way to control where their blocks appear in the inserter relative to other blocks in the same category. This makes it difficult to surface important custom blocks prominently. The inserterPriority property gives developers control over block ordering within the inserter.

How?

1. Added inserterPriority property to the block.json schema (schemas/json/block.json)
2. Added inserterPriority to allowed fields in JS block registration (packages/blocks/src/api/registration.js)
3. Modified the store reducer to merge bootstrapped data (packages/blocks/src/store/reducer.js)
4. Added sorting logic in getInserterItems selector (packages/block-editor/src/store/selectors.js)
5. Created PHP compat file to pass inserterPriority from server to client (lib/compat/wordpress-6.9/block-inserter-priority.php)

Blocks with lower inserterPriority values appear first. Default is 0.

Testing Instructions

1. Create a plugin with a custom block that includes inserterPriority in its block.json:

   {
     "name": "my-plugin/priority-block",
     "title": "Priority Block",
     "category": "widgets",
     "inserterPriority": -10
   }

2. Activate the plugin and open the block editor.
3. Open the Block Inserter and navigate to the "Widgets" category.
4. Verify the block with inserterPriority: -10 appears before other blocks in the category.
5. In the browser console, verify:

   wp.data.select('core/block-editor').getInserterItems()
     .filter(i => i.name.startsWith('my-plugin/'))
     .map(i => `${i.name}: ${i.inserterPriority}`)

Testing Instructions for Keyboard

1. Open the block editor and press / to open the slash inserter.
2. Type a block name to filter results.
3. Use arrow keys to navigate the list.
4. Verify blocks are ordered by their inserterPriority value (lower values first).

Screenshots or screencast

Before: Blocks ordered by registration	After: Blocks ordered by inserterPriority (lower values first)

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Co-authored-by: Vrishabhsk <vrishabhsk@git.wordpress.org>
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[Mamaduka]

Thanks for contributing, @Vrishabhsk! Closing this based on the discussion in the issue.