Add missing filenames for Node 12 imports

src/core/operations/Lorenz.mjs

@@ -6,8 +6,8 @@
  * @license Apache-2.0
  */
 
-import Operation from "../Operation";
-import OperationError from "../errors/OperationError";
+import Operation from "../Operation.mjs";
+import OperationError from "../errors/OperationError.mjs";
 
 /**
  * Lorenz operation