Do not run sanity check on rails generate stimulus_reflex:config

If a sanity check fails, the user gets a hint to create the configuration file with
`rails generate stimulus_reflex:config`, however this command will also fail because it
will also run the sanity check. Therefore we have to bypass the sanity check if
the caller is a `generate_command`.

lib/stimulus_reflex.rb

@@ -21,7 +21,13 @@
 module StimulusReflex
   class Engine < Rails::Engine
     initializer "stimulus_reflex.sanity_check" do
-      SanityChecker.check!
+      SanityChecker.check! unless called_by_generate_command?
+    end
+
+    private
+
+    def called_by_generate_command?
+      caller.any? { |call| call.match("generate_command") }
     end
   end
 end