Reads a use declaration
```ebnf
use_declaration ::= use_type? namespace_name use_alias
```
@see https://github.com/php/php-src/blob/master/Zend/zend_language_parser.y#L380
@return {UseItem}
function(typed) {
    const result = this.node("useitem");
    let type = null;
    if (typed) type = this.read_use_type();
    const name = this.read_namespace_name();
    const alias = this.read_use_alias();
    return result(name.name, alias, type);
  }