Editor: Allow registration of blocks that include assets from within a theme

Fixes the issue when you register blocks with `block.json` in your theme. There is no longer an assets's URL error because it resolves correctly in relation to the theme where it is located.

Props fabiankaegy, ocean90, whoisnegrello, audrasjb, peterwilsoncc, 
Fixes #54647, #55513.



git-svn-id: https://develop.svn.wordpress.org/trunk@53091 602fd350-edb4-49c9-b593-d223f7449a82

tests/phpunit/data/themedir1/block-theme/blocks/example-block/block.json

@@ -0,0 +1,8 @@
+{
+	"apiVersion": 2,
+	"title": "Example Theme Block",
+	"name": "block-theme/example-block",
+	"description": "Custom block registered from within a theme",
+	"editorScript": "file:./index.js",
+	"style": "file:./style.css"
+}

tests/phpunit/data/themedir1/block-theme/blocks/example-block/editor-style-rtl.css

@@ -0,0 +1 @@
+/* Test CSS file - RTL version */

tests/phpunit/data/themedir1/block-theme/blocks/example-block/editor-style.css

@@ -0,0 +1 @@
+/* Test CSS file */

tests/phpunit/data/themedir1/block-theme/blocks/example-block/index.asset.php

@@ -0,0 +1,6 @@
+<?php
+
+return array(
+	'dependencies' => array( 'wp-element', 'wp-blocks' ),
+	'version'      => 'test',
+);

tests/phpunit/data/themedir1/block-theme/blocks/example-block/index.js

@@ -0,0 +1 @@
+/* Test JavaScript file. */

tests/phpunit/data/themedir1/block-theme/blocks/example-block/style-rtl.css

@@ -0,0 +1 @@
+/* Test CSS file - RTL version */

tests/phpunit/data/themedir1/block-theme/blocks/example-block/style.css

@@ -0,0 +1 @@
+/* Test CSS file */

tests/phpunit/data/themedir1/block-theme/blocks/example-block/view.asset.php

@@ -0,0 +1,6 @@
+<?php
+
+return array(
+	'dependencies' => array( 'wp-element', 'wp-blocks' ),
+	'version'      => 'test',
+);

tests/phpunit/data/themedir1/block-theme/blocks/example-block/view.js

@@ -0,0 +1 @@
+/* Test JavaScript file. */

tests/phpunit/data/themedir1/block-theme/functions.php

@@ -0,0 +1,7 @@
+<?php
+
+add_action( 'init', 'register_theme_blocks' );
+
+function register_theme_blocks() {
+	register_block_type( __DIR__ . 'blocks/example-block' );
+}