feat(e2e): create basic e2e test runner

This is mostly PoC code that shows how this can be done. This will grow
into the actual test runner.

packages/core/src/components/button/test/button.e2e-spec.ts

@@ -0,0 +1,5 @@
+describe('buttons', () => {
+  it('loads', () => {
+
+  });
+});