Allow numerics for templates using code_maybe_block

A number of ERB templates use the code_maybe_block method
to assist with formatting. This fails if the value being
passed is not a string, such as an integer default value
for a resource type.

lib/puppet-strings/markdown/helpers.rb

@@ -12,7 +12,7 @@ module PuppetStrings::Markdown::Helpers
   # @param [String] inline_prefix String to insert before if it’s inline.
   # @returns [String] Markdown
   def code_maybe_block(code, type: :puppet, block_prefix: "\n\n", inline_prefix: ' ')
-    if code.include?("\n")
+    if code.to_s.include?("\n")
       "#{block_prefix}```#{type}\n#{code}\n```"
     else
       "#{inline_prefix}`#{code}`"