chore(monorepo/client): move client source files

apps/client/src-example/app/app.element.spec.ts

@@ -0,0 +1,21 @@
+import { AppElement } from './app.element';
+
+describe('AppElement', () => {
+  let app: AppElement;
+
+  beforeEach(() => {
+    app = new AppElement();
+  });
+
+  it('should create successfully', () => {
+    expect(app).toBeTruthy();
+  });
+
+  it('should have a greeting', () => {
+    app.connectedCallback();
+
+    expect(app.querySelector('h1').innerHTML).toContain(
+      'Welcome @triliumnext/client'
+    );
+  });
+});