Feature request: Make File transport create log dir if it doesn't exist

[DABH]

What's the feature?

I've seen several times people confused their log files don't appear (e.g. #875) because the dir into which they want to write files doesn't exist. So I think we should allow winston to automatically create the log dir -- either as an option to the File transport, or even as the default behavior (with an option to disable). @indexzero can advise whether it should be a default or not.

What problem is the feature intended to solve?

Multiple GitHub issues for winston about this, it trips up users

Is this a feature you're prepared to implement, with support from us?

@JamesTheHacker has indicated interest in creating a PR for this! 🚀

[adoyle-h]

@DABH I have committed a PR to resolve this issue. Please review the codes.