Sprinkle frozen string literal & Indentation Fix (#150)

* Avoid extra string alocation as join will always return string

* Fix indentation

* Sprinkle frozen string literal true

lib/custom_exceptions/account.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module CustomExceptions::Account
 
   class InvalidEmail < CustomExceptions::Base

lib/custom_exceptions/base.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class CustomExceptions::Base < ::StandardError
 
   def to_hash

lib/custom_exceptions/report.rb

@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module CustomExceptions::Report
   class InvalidIdentity < CustomExceptions::Base
     def message