Patch for Rails 7

Documented in #59. This class was removed from Rails 7. 

This causes an error on this line when trying to alias a method that does not exist https://github.com/zombocom/maildown/blob/cbf5b51e0867eab1ec945d38b5335f42139b0322/lib/maildown/ext/action_view.rb#L7.

The solution presented was to re-add the method. However simply doing this with a `defined?(OptimizedFileSystemResolver)` causes a load via zeitwork and also results in a crash.

The presence of this code appears to do nothing in Rails 7. It's basically a no-op that allows us to boot without erroring.

lib/maildown/ext/action_view.rb

@@ -1,5 +1,20 @@
 # frozen_string_literal: true
 
+if !defined?(ActionView::OptimizedFileSystemResolver)
+  module ActionView
+    # https://github.com/codetriage/maildown/issues/59
+    #
+    # extract_handler_and_format_and_variant was removed in https://github.com/rails/rails/commit/2be8d3ebf85e26e936a7717b968737ee333d95bd
+    # OptimizedFileSystemResolver was removed in https://github.com/rails/rails/commit/faac734387124c6d780dbfcfdab721b2f26ce865
+    class OptimizedFileSystemResolver < FileSystemResolver
+      def extract_handler_and_format_and_variant(template)
+        details = @path_parser.parse(template)
+        [details.handler, details.format, details.variant]
+      end
+    end
+  end
+end
+
 # This monkeypatch allows the use of `.md.erb` file extensions
 # in addition to `.md+erb` and `.md`
 module ActionView