[NEOS-1328] Give users a JS playground to write their transformers

[nickzelei]

Might be easier to do for the generator, but for the transformer we have to figure out the type that will be inserted based on the Go type of the object value coming in from benthos.

If we can figure this out, we can give users tools to help themselves debug JS transformers directly in the browser and are less likely to need our input.

_{From SyncLinear.com | NEOS-1328}