adding missing file

vitest.setup.ts

@@ -0,0 +1,28 @@
+
+// adding this for the "TypeError: window.matchMedia is not a function" error
+// see https://github.com/vitest-dev/vitest/issues/821
+
+import { vi } from 'vitest';
+
+
+Object.defineProperty(window, 'matchMedia', {
+    writable: true,
+    value: vi.fn().mockImplementation((query) => ({
+      matches: false,
+      media: query,
+      onchange: null,
+      addListener: vi.fn(),
+      removeListener: vi.fn(),
+      addEventListener: vi.fn(),
+      removeEventListener: vi.fn(),
+      dispatchEvent: vi.fn(),
+    })),
+  });
+
+  class ResizeObserver {
+    observe() {}
+    unobserve() {}
+    disconnect() {}
+  }
+
+  window.ResizeObserver = ResizeObserver;