Make .delay method work with ActionMailer::Parameterized::Mailer

This PR unifies the DelayedJob behavior of ActionMailer::Base and ActionMailer::Parameterized::Mailer

Now, the following syntax works equivalently:

```ruby
# works currently
MyMailer.delay.my_method

# this PR makes the following work
MyMailer.with(foo: 1, bar: 2).delay.my_method
```

Note that ActionMailer::Parameterized::Mailer does not inherit ActionMailer::Base (moreover, the `.with()` method returns an object instance, hence we use `include` rather than `extend`)

lib/delayed_job.rb

@@ -16,6 +16,7 @@
 ActiveSupport.on_load(:action_mailer) do
   require 'delayed/performable_mailer'
   ActionMailer::Base.extend(Delayed::DelayMail)
+  ActionMailer::Parameterized::Mailer.include(Delayed::DelayMail)
 end
 
 module Delayed