Added cypress test

cypress/integration/rendering/marker_unique_id.spec.js

@@ -0,0 +1,10 @@
+import { urlSnapshotTest } from '../../helpers/util.ts';
+
+describe('Marker Unique IDs Per Diagram', () => {
+  it('should render a blue arrow tip in second digram', () => {
+    urlSnapshotTest('http://localhost:9000/marker_unique_id.html', {
+      logLevel: 1,
+      flowchart: { htmlLabels: false },
+    });
+  });
+});