add_render_attribute should treat boolean values as boolean attributes

Prerequisites • I have searched for similar features requests in both open and closed tickets and cannot find a duplicate. • The feature is still missing in the latest stable version of Elementor ( Elementor Pro ) What problem is your feature request going to solve? Please describe. If you provide an a value of boolean false to an attribute in Controls_Stack::add_render_attribute, then get_render_attribute_string still prints that attribute name with no value. This is contrary to HTML's concept of a "boolean attribute", for which <img data-attribute /> has a _true_ boolean attribute of data-attribute, and only <img /> has that attribute as false. Describe the solution you'd like These lines in the add_render_attribute function: ...should be something more like this to properly handle a boolean false: Describe alternatives you've considered I know that solution could have side effects on existing code, so…