Support `include` directives

[parsonsmatt]

The yaml package has a Data.Yaml.Include API which allows you to use include directives to reference other files.

We want to use this to allow us to have an hlint-rules directory, and different teams can own their own hlint rules via CODEOWNERS. This way, they can be in charge of their own rules, and any modification or exclusion of those rules would trigger review for the relevant team.

[zliu41]

That sounds quite useful, thanks for the idea!

[parsonsmatt]

So, it is also possible to pass multiple hlint files with --hint. I may go this route instead as #1639 means I can't import these in groups.