bump version

Former-commit-id: a72d11f9f53509cd8de66749bf957f5440047a68

manifest.json

@@ -8,7 +8,7 @@
 		"64": "extension/ui/resources/icon_64.png",
 		"128": "extension/ui/resources/icon_128.png"
 	},
-	"version": "1.13.20",
+	"version": "1.13.21",
 	"description": "__MSG_extensionDescription__",
 	"content_scripts": [
 		{