Add test for invert function to verify key-value swapping behavior

Author: alexandru-pocovnicu

Sprint-2/interpret/invert.test.js

@@ -0,0 +1,4 @@
+const invert = require("./invert.js");
+test("swap the keys and values in the object", () => {
+  expect(invert({ a: 1, asd: "d3e" })).toEqual({ 1: "a", d3e: "asd" });
+});