add index page (#73)

add index page

apps/deno-vless/src/app/app.spec.tsx

@@ -0,0 +1,17 @@
+import { render } from '@testing-library/react';
+
+import App from './app';
+
+describe('App', () => {
+  it('should render successfully', () => {
+    const { baseElement } = render(<App />);
+
+    expect(baseElement).toBeTruthy();
+  });
+
+  it('should have a greeting as the title', () => {
+    const { getByText } = render(<App />);
+
+    expect(getByText(/Welcome test-app/gi)).toBeTruthy();
+  });
+});