Support for ignoring external $ref pointers

[noc7c9]

Detailed description

Is it possible to $ref pointers to external schemas to be ignored during the resolving phase?

Context

We have a few references to external schemas that we don't really care about linting and in this case they don't actually exist yet so the resolution fails.

[philsturgeon]

Looks like --internal-options is the way to go, its just not documented. #373

Maybe you could close this issue, and make a PR adding it to the docs, which will also close #373 if anyone gets around to merging it.

[noc7c9]

Sorry of the delay in responding to this. Unfortunately I'm not sure when I'll be able to look into this as I've moved onto other projects in the meantime. I intend to come back to this eventually, but it might be some time.