Additional config for ignoring "unresolvable licence"

[jonasps]

Hello and thank you for your work with lichen!

I’m currently in need of running lichen in environments where a substantial amount of "unresolvable licence" errors can happen (running it as part of a tool for other developers to use at my company). In my case returning an empty licence is a much better default than returning an error. And there might be others with similar needs so I suggest we add a config for this?

I have two different suggestions for additional configs:

A:

ignoreUnresolvableLicense: true
Would result in ´func ignoreUnresolvable()´ always returning true.

Or B:

unresolvableLicense:
 - regex: true 
 - path: "github.com/test/.*"

regex: true would result in unresolvableLicense's path beeing a regular expression.

Which of these suggestions would be best for lichen?

I can create a PR with this if you wan't to test it in practice, the additional code will be short.