Support magic import path for "generated" schemas

[milesj]

The generated shapeshifter file (usually an index.js file) encounters a ton of churn any time a schema changes. This can cause merge conflicts when 2 separate branches generate a new output file.

Perhaps support a magic import path, like import { SomeShape } from 'shapeshifter/schemas';, which will automatically generate the shapeshifter file during a build process (webpack), instead of including the generated file in the source code.

Pros:

• No build command needs to be run
• No file committed to source
• No possibility of conflicts

Cons:

• Breaks IDE/editor import lookups and references
• Not apparent whether a schema/type/constant is supported (unless looking for the JSON files)