prototype runtime isn't aware of extend

[pocke]

rbs prototype runtime command ignores extend.
For example:

# test.rb

module M
end

class C
  extend M
end

$ rbs prototype runtime -R test.rb M C
class C
end

module M
end

Class C is extended with module M, but the generated RBS doesn't have the extended module.

I expect the following output.

$ rbs prototype runtime -R test.rb M C
class C
  extend M
end

module M
end

---

prototype rb generates RBS with extend expectedly.

# with the same test.rb

$ rbs prototype rb test.rb
module M
end

class C
  extend M
end