Rule Suggestion: disallow explicit boolean comparisons

[ChrisMBarr]

Novice programmers might have something like this

let foo = true;
// other code...

if (foo === true) {
  //do something...
}

or maybe

if (foo !== false) {
  //do something...
}

(I have seen both of these in real code!)

When foo is a boolean, this is unnecessary and could result in a linting violation. However if foo can be something else like foo: true | number | null then these explicit checks should be allowed.

perhaps this could be added as an option to the existing strict-boolean-expressions rule?