[feature-request] Add screaming snake case

[jezhou]

Thank you for writing this extension! It has definitely saved me a lot of time.

I write a lot of Ruby and sometimes have to constantize some variables by first changing the variable to snake case, and then to uppercase. I think SCREAMING_SNAKE_CASE is a thing in RubyMine, so it would be awesome if I could just do it in one command like in RubyMine instead of two.

Would be happy to make a PR if sounds like a good idea 🙂

[globalhuman]

Are you after CONSTANT_CASE which is implemented already?

I think SCREAMING_SNAKE_CASE is an alternative name