Include "value only" flag for `bake`

**Is your feature request related to a problem? Please describe.**
Currently when you POST to `/bake` it returns a type and a value. If someone wanted to write the converted input to file, they would need to do some post-processing to extract the value from the returned data.

There could be a `valuesOnly` flag or property that the user could set, and then only the value would be returned.

**Describe the solution you'd like**
if `valuesOnly` is truthy
return body only contains dish.value
`outputType` is still honoured