Introduce a `stylistic` config

[JasonWeinzierl]

A handful of rules in this plugin are opinionated suggestions that could be combined into a stylistic config.

The following would be added:

• finnish
• no-explicit-generics
• suffix-subjects
• no-subject-value ?

The following would be removed from strict and added to stylistic instead:

• no-exposed-subjects ? (change type from problem to suggestion)
• no-unnecessary-collection ?

Thoughts?