Lint config is a bit stupid with return types

[samhh]

Explicit return types are good, but it should also accept them when they're provided via a previous (for want of a better word) type. For example, the following is completely safe and explicit, but the linter flags it:

const startsWith = (x: string): Predicate<string> => (y) => y.startsWith(x);

[samhh]

typescript-eslint/typescript-eslint#928