fix: add transform strign

Author: HerringtonDarkholme

website/public/schema.json

@@ -560,6 +560,9 @@
     "Transformation": {
       "description": "Represents a transformation that can be applied to a matched AST node. Available transformations are `substring`, `replace` and `convert`.",
       "oneOf": [
+        {
+          "type": "string"
+        },
         {
           "type": "object",
           "required": [