Add Napi bindings js part generation too

[noartem]

For now, c++ part of bindings is generated automatically from js-based DSL. It would be awesome to generate JS-part (lib/elementor.ts) too.

Default method implementation will be transformed from C++ part:

1. JS Arguments types will be cast from c++ arguments:

C++	JavaScript
std::string	string
int	number
float	number
Size	Size
Element	Element

2. Default method implementation will be something like this:

class ClassName {
  methodName(...args) {
    super.methodName(...args);
    return this;
  }
  methodName(...args) {
    return super.methodName(...args); // if body last line starts with return
  }
}