Add JavaScript Language to API Explorer

Is your feature request related to a problem?

I am looking to use this amazing plugin, but require a JavaScript language option in the API Explorer. I see the codegen in your plugin, but its not being utilized in the component.

Describe the solution you'd like

I would like the JavaScript language to be an option in the API Explorer, specifically js-fetch, although the more the merrier.

Describe alternatives you've considered

Using a different method of displaying docs, although I really don't want to.

Additional context

I would be happy to open a PR to assist with this, if you can provide some direction on getting it working. I messed around locally, but it kept crashing.