[json-schema-loader] Breaks Webpack 2

As per the most recent commit - https://github.com/cloudflare/json-schema-loader/commit/2e75f223a77c987b66e98d054c3018d3e64f93dc - this now breaks for webpack 2.

The docs specify that callback should be invoked with a second argument that looks like a sourcemap, not an arbitrary type. https://webpack.js.org/api/loaders/#this-callback.

We are able to use 0.0.3 and it works, but you might want to specify webpack version in the readme.

[handrews]

@wmonk if we decide we don’t need json-schema-loader in the doca suite, we would still likely fix it for webpack 2 and keep it as an active project, we’d just change it to be standalone and give it its own issues list, etc.

[handrews]

json-schema-loader has been deprecated in favor of the new @cloudflare/json-schema-ref-loader in the https://github.com/cloudflare/json-schema-tools repository. @cloudflare/json-schema-ref-loader does not use the extra parameter. The requested bundling feature is tracked as cloudflare/json-schema-tools#2