Support persisted query file generation

[dr3]

Great package btw, works really well with dev servers!

The manual running of the compiler accepts the the --persist-output flag to generate the persisted queries file, however I do not see a method to do so using this package.

Is this something that could potentially be supported?

[danielholmes]

@dr3 yea definitely. I'm not working on any relay projects atm so don't have a desire to implement it. Would accept a PR though if you or someone else has time for the work.

[sorenhoyer]

@dr3 Can't you just pass it to the nested config object? Just like you'd do with noFutureProofEnums and others? Should work already, although that nested config object seems a bit weird. Opened an issue regarding it.