Any plans for adding $ref input support to external files?

[dpwdec]

I was wondering if there's any planned worked for updating $ref parsing in spec to read in external files?

I've been looking through the current code base and can see where this functionality could be added. But I didn't want to start doing the work if its duplicated effort that someone else on the project is already working on.

I think this would be valuable addition as its standard AsyncAPI practice to have a single definition file per service and then for those service files to share message definitions and schemas rather than trying to duplicate and synchronise those definitions with internal components object.

Hoping to add support for external files that are stored on the local file system as that is more common I believe rather than doing some sort of fetch to an external repository, however in the future this might also be valuable to make the library fully featured.

[VisualBean]

Someone awesome totally added this support already #131