Support Header in request chaining

I'm currently working in an API that returns the Authorization Token in a header in the sign in response, so instead of getting the token in the response body or in a cookie i want to get from a header, after some investigation i've managed to create a plugin (https://github.com/ceopaludetto/yaak-plugin-header) but would be awesome if this plugin was actually pre installed for everyone. Feel free to copy the source code (I didn't open a PR since the guidelines says that only bug fixes are allowed)