Add yaml support (#7)

rswag-specs/lib/generators/rswag/specs/install/templates/swagger_helper.rb

@@ -32,4 +32,10 @@ RSpec.configure do |config|
       ]
     }
   }
+
+  # Specify the format of the output Swagger file when running 'rswag:specs:swaggerize'.
+  # The swagger_docs configuration option has the filename including format in
+  # the key, this may want to be changed to avoid putting yaml in json files.
+  # Defaults to json. Accepts ':json' and ':yaml'.
+  config.swagger_format = :yaml
 end