Add workflow for pushing to Ruby Gems
Add workflow for pushing to Ruby Gems

Creates a workflow for publishing to the public Zendesk RubyGems
account.

Uses the workflow from the public `gw` gem. `gw`'s (ruby-gem-publication readme](https://github.com/zendesk/gw/blob/main/ruby-gem-publication/README.md)

zendesk/active_record_host_pool