Add explicit requires for riiif constants

In development we were seeing the Universal Viewer locking up the entire
web service when trying to load certain riiif constants.  This commit
will load those contants beforehand in an initializer.

config/initializers/riiif.rb

@@ -1,4 +1,12 @@
 # frozen_string_literal: true
+
+# Loading these constants during runtime would freeze the web service in development.
+# Adding the requires here to load them on initialize.
+require 'riiif/imagemagick_transformer'
+require 'riiif/imagemagick_command_factory'
+require 'riiif/crop'
+require 'riiif/resize'
+
 Rails.application.reloader.to_prepare do
   Riiif::Image.info_service = lambda do |id, _file|
     # id will look like a path to a pcdm:file