add diagram renderer mocks

__mocks__/requirementRenderer.js

@@ -0,0 +1,13 @@
+/**
+ * Mocked requirement diagram renderer
+ */
+
+import { vi } from 'vitest';
+
+export const draw = vi.fn().mockImplementation(() => {
+  return '';
+});
+
+export default {
+  draw,
+};