[Community localization checklist] Add warning when a component does not have Source string bug reporting address set up

[emmapeel2]

To allow for a seamless integration of translations in a project, and to allow for translators to become source string reviewers and contribute upstream, it makes a lot of sense to have an email for the source strings reports. In Tor Project we have it configured to mail our translators mailing list, although the bot is not subscribed so their contributions are moderated.

In the "Building Community" section a note could be added for mantainers to add an email. I have noticed that many maintainers do not realise of this useful feature, but will readily add it when informed.