Rule proposal: Warn on duplicate props

[Markus-ipse]

When you're in strict-mode you get warnings when you have duplicate properties in an object, a similiar warning for props on React components would be nice.

return (
   <Mycomponent className={classes}
                            onClick={this.handleClick}
                            someOtherProp={stuff}
                            onClick={this.onClick} /> // Duplicate prop, should produce an ESLint error
);

[mathieumg]

👍 +1