add headers in desc support

[Skipper1992]

No description provided.

[falood]

Thank you, it's a good idea!
I think we can not just make header a part of description, we can make it works as the same as params, parse parameters from header and generate document.
The DSL should be like this:

desc "this is description" 
header do
  requires :session_id, type: String
end
params do
  requires :param1, type: Integer
end
post do
  ...
end

[jalcine]

Hey @Skipper1992; are you considering incorporating the feedback above?

[jalcine]

It looks like this was slightly abandoned. If you're cool with it @falood, I can re-open a new PR for this.