New rule: Lint against modifier which does not use the element

[chrisrng]

Why: This is simply abusing modifiers to make them behave like observers (cc @chriskrycho)

If a class-based modifier:

• If using any method other than modify, check for use of this.element.
• If using modify, check for use of the first argument, which is always the element.

If a function-based modifier: check for use of the first argument, which is always the element.

Sample error case:

import Modifier from 'ember-modifier';

export default class WrongModifier extends Modifier {
  didReceiveArguments() {
    if (this.args.named.shouldFire) {
      this.args.named.myCallback?.();
    }
  }
}

Sample success case:

import Modifier from 'ember-modifier';

export default class ScrollPositionModifier extends Modifier {
  modify(element, [scrollPosition], { relative }) {
    if(relative) {
      element.scrollTop += scrollPosition;
    } else {
      element.scrollTop = scrollPosition;
    }
  }
}