docs: add some comments

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

@@ -41,27 +41,30 @@ module Fastlane
           UI.user_error!("❌ Ios credentials doesn't exist")
           puts("json file doesn't exist")
         end
+      end
 
-        def self.check_required_fields(required_fields, json)
-          missing_fields = required_fields - json
+      # Check json fields
+      def self.check_required_fields(required_fields, json)
+        missing_fields = required_fields - json
 
-          unless missing_fields.empty?
-            raise ArgumentError, "❌ missing keys in credential json file : #{missing_fields}"
+        unless missing_fields.empty?
+          raise ArgumentError, "❌ missing keys in credential json file : #{missing_fields}"
+        end
+      end
+
+      # Check if set of environment variables are defined
+      def self.check_environment_variables(variables)
+        variables.each do |variable|
+          unless ENV.key?(variable)
+            raise "❌ The environment variable '#{variable}' is not defined."
           end
         end
+      end
 
-        def self.check_environment_variables(variables)
-          variables.each do |variable|
-            unless ENV.key?(variable)
-              raise "❌ The environment variable '#{variable}' is not defined."
-            end
-          end
-        end
-
-        def self.delete_artifacts(artifacts)
-          artifacts.each do |file|
-            File.delete(file) if File.exist?(file)
-          end
+      # Delete built files
+      def self.delete_artifacts(artifacts)
+        artifacts.each do |file|
+          File.delete(file) if File.exist?(file)
         end
       end
     end