feat: added unknown method schema

Author: AndyOGo

schemas/operators/misc/method.json

@@ -1,4 +1,15 @@
 {
   "$schema": "http://json-schema.org/draft-04/schema#",
-  "$id": "http://jsonlogic.com/schemas/operators/misc/method.json"
+  "$id": "http://jsonlogic.com/schemas/operators/misc/method.json",
+
+  "title": "method",
+  "description": "Unknown, not documented.",
+  "type": "object",
+  "additionalProperties": false,
+  "required": ["method"],
+  "properties": {
+    "method": {
+      "$ref": "http://jsonlogic.com/schemas/common/any.json"
+    }
+  }
 }