Add Truffleruby support to CI

[gogainda]

No description provided.

[tubbo]

The only test in this whole repo is https://github.com/redis-store/redis-rails/blob/master/test/redis_rails_test.rb, so I'm thinking this would be better off in the https://github.com/redis-store/redis-store repo. We don't have GItHub Actions set up for that repo yet so I will see what I can do about that.