qmlls: completion for JS variables

    function test1() {
        for (unexistingVar = 424242; unexistingVar < 0; ++i){
        }
        // fine, because no let/var/const
        console.log(unexistingVar);
    }
    function test2() {
        for (var scopedVar = 123; scopedVar2<0; ++i){
        }
        // not fine: Uncaught ReferenceError: scopedVar2 is not defined
        console.log(scopedVar);
    }