[FIX] qweb: re-add test on memory leak

Re-add test from 6e185f9.

tests/qweb/qweb_memory.test.ts

@@ -0,0 +1,12 @@
+import { renderToString, snapshotEverything } from "../helpers";
+
+snapshotEverything();
+
+describe("memory", () => {
+  test("t-foreach does not leak stuff in global scope", () => {
+    const initialNumberOfGlobals = Object.keys(window).length;
+    const template = `<p><t t-foreach="[3, 2, 1]" t-as="item" t-key="item_index"><t t-esc="item"/></t></p>`;
+    expect(renderToString(template)).toBe("<p>321</p>");
+    expect(Object.keys(window).length).toBe(initialNumberOfGlobals);
+  });
+});