Provide an example Trame application for visual/manual testing

This adds a simple test Trame application that shows a set of commonly used Vuetify components that can be used to visually test the themes we develop here. The test page is fairly bland right now but should become better once I've moved my work on https://code.ornl.gov/ndip/trame-apps/trame-app-launcher/-/tree/28-allow-the-user-to-swap-between-curated-themes?ref_type=heads to this repo as it will allow us to preview multiple themes inside of this test page.

I've also added some simple instructions to the README for running the test application. I haven't included any Docker builds as I don't think this application should ever run in a production environment.

Closes #6 (closed)