add @wordpress/widget-types to docs manifest

Author: retrofox

docs/manifest.json

@@ -2129,6 +2129,12 @@
 		"markdown_source": "../packages/warning/README.md",
 		"parent": "packages"
 	},
+	{
+		"title": "@wordpress/widget-types",
+		"slug": "packages-widget-types",
+		"markdown_source": "../packages/widget-types/README.md",
+		"parent": "packages"
+	},
 	{
 		"title": "@wordpress/widgets",
 		"slug": "packages-widgets",