Ensure nothing is explicitly typed as "any"

[mxstbr]

While Flow has its linter, which has a setting that nothing can be typed as "any", that's unfortunately not very applicable in the real-world as you'll encounter tons of dependencies that are untyped and it's simply not feasible to type them all.

Instead, this plugin should check and make sure that nothing is explicitly typed as any in the code. (maybe also include Object since it's too generic?)