Please describe what the rule should do:

Forbid return statements in constructors.

What category of rule is this? (place an "X" next to just one item)

[x] Suggests an alternate way of doing something (suggestion)

Provide 2-3 code examples that this rule will warn about:

class Foo {
  constructor () {
    return Math;
  }
}

class Goo {
  constructor () {
    return this;
  }
}

Why should this rule be included in ESLint (instead of a plugin)?

In Javascript return value in constructor is allowed, and the return value is the evaluated value when the class is new-ed. A class created with pattern behaves very differently from a normal class in the OOP paradigm, for example, in that every new instance should be a separate object. There seemed to be no practical usage of this pattern. Forbidding this pattern prevents mistake resulting from unfamiliarity with the language or copy-paste error.

Are you willing to submit a pull request to implement this rule?

Possibly.