Async Promise
To see the demo, start a web server and load this page (e.g., `npx http-server` and navigate to http://127.0.0.1:8080/demos/async-promise.html).
Using vexflow-core.js allows your webpage to load a smaller initial bundle. It will load fonts on demand
when you call VexFlow.loadFonts(...fontNames)
. This method is asynchronous and returns a Promise.
Open your browser's developer tools to see that font files are downloaded upon request:
View this page's source code for more information.