Parcel 2: Reason transformer

[devongovett]

Create the @parcel/transformer-reason package in packages/transforms/reason. This package is a Parcel 2 transform plugin for Reason. It should be based on the ReasonAsset from Parcel 1.

The @parcel/transformer-reason package is responsible for the following things:

• Compiling Reason to JavaScript with bsb-js
• Collecting dependencies as included files so Parcel watches them (Parcel 1 does not currently do this properly)