Fix block.json schema

schemas/json/block.json

@@ -346,6 +346,22 @@
 						}
 					}
 				},
+				"background": {
+					"type": "object",
+					"description": "This value signals that a block supports some of the CSS style properties related to background. When it does, the block editor will show UI controls for the user to set their values if the theme declares support.\n\nWhen the block declares support for a specific background property, its attributes definition is extended to include the style attribute.",
+					"properties": {
+						"backgroundImage": {
+							"type": "boolean",
+							"description": "Allow blocks to define a background image.",
+							"default": false
+						},
+						"backgroundSize": {
+							"type": "boolean",
+							"description": "Allow blocks to define values related to the size of a background image, including size, position, and repeat controls",
+							"default": false
+						}
+					}
+				},
 				"html": {
 					"type": "boolean",
 					"description": "By default, a block’s markup can be edited individually. To disable this behavior, set html to false.",