Just start an http server from the project root (for example, with python3 -m http.server). Then open localhost:<port> in a web browser, where <port> is the port number for your server.
To enable some debugging helpers, uncomment debugSetup() in main.js. Then you can use the JS console to add and remove text from the window.
- Only tested in Chrome for now, might look unpleasant in other browers.