Add Stopgap JSON Serialisation

[iamrecursion]

Summary

Implement a stopgap solution for serialising Enso data to JSON in order to allow IDE to display JSON visualisations under the hood.

Value

A stopgap solution for serialising Enso objects to JSON will allow IDE to complete this portion of their integration sooner.

Specification

Please note that this stopgap solution only allows for serialisation, and not deserialisation.

• The temporary toJSON : Any -> Text will return a JSON string.
• Implement a generic toJSON on Any as a builtin in the interpreter.
• This should be backed by a Java implementation.

Acceptance Criteria & Test Cases

• We have a way of serialising Enso objects to JSON implemented in the runtime.
• The serialisation functionality produces well-formed JSON and is tested to do so.