docs: add some comments

plugins/fastlane-plugin-ios_cd/lib/fastlane/plugin/ios_cd/helper/ios_cd_helper.rb

@@ -41,7 +41,9 @@ module Fastlane
           UI.user_error!("❌ Ios credentials doesn't exist")
           puts("json file doesn't exist")
         end
+      end
 
+      # Check json fields
       def self.check_required_fields(required_fields, json)
         missing_fields = required_fields - json
 
@@ -50,6 +52,7 @@ module Fastlane
         end
       end
 
+      # Check if set of environment variables are defined
       def self.check_environment_variables(variables)
         variables.each do |variable|
           unless ENV.key?(variable)
@@ -58,6 +61,7 @@ module Fastlane
         end
       end
 
+      # Delete built files
       def self.delete_artifacts(artifacts)
         artifacts.each do |file|
           File.delete(file) if File.exist?(file)
@@ -66,4 +70,3 @@ module Fastlane
     end
   end
 end
-end