codesandbox.io integration

Codesandbox.io could be a great platform for doing hyperstack UI work, demo's etc.

Here is an example https://codesandbox.io/s/upbeat-ives-k3yfd

Not much there, but it shows how to get Opal loaded into the system.

The next steps are to look at how the "parcel" npm bundler works (as that is what they use) and add ability to compile opal to parcel. See https://parceljs.org/asset_types.html to start understanding what to do.

Looks like there are great examples, with other languages (i.e. Rust) so seems doable.