webui: Demo of parsing / generating

[adamdecaf]

We could create a WASM / webui demo of parsing card data / track data. It would be helpful for folks to paste in captured data and get the JSON results out.

Similar to https://oss.moov.io/ach/

[alovak]

it's possible if:

• their message is packed using the spec we have in ./specs
• we will allow them to put json spec into the UI
  thoughts?