Merge pull request #21678 from ronakjangir47/array_to_formatted_s_docs

Added Examples in docs for internal behavior of Array#to_formatted_s [ci skip]

activesupport/lib/active_support/core_ext/array/conversions.rb

@@ -86,6 +86,8 @@ class Array
   # comma separated id list if <tt>:db</tt> argument is given as the format.
   #
   #   Blog.all.to_formatted_s(:db)  # => "1,2,3"
+  #   Blog.none.to_formatted_s(:db) # => "null"
+  #   [1,2].to_formatted_s          # => "[1, 2]"
   def to_formatted_s(format = :default)
     case format
     when :db