This PR enables custom email dark mode styles by default that were added here.
There is currently poor support for dark mode queries in mail clients. The main beneficiary of these changes will be Apple Mail and Outlook.
Enjoy the darkness 🕶️
It's very easy to forget to add `require 'rails_helper'` at the top of every core/plugin spec file, and omissions can cause some very confusing/sporadic errors.
By setting this flag in `.rspec`, we can remove the need for `require 'rails_helper'` entirely.
