[Community localization checklist] Add warning when a component does not have any user receiving notifications for repository errors

[emmapeel2]

In hosted.weblate.org and maybe in other weblate instances too, some components are not actively mantained, or have lost connection to their upstreams and are failing.

For translators this is quite frustrating, see for example #8276 but there are many instances.

Oftentimes this is not the intention of the maintainers, but there is a lack of communication or they haven't realised they need to set up notifications for the component.

So, I suggest that the Community Localization Checklist provide a warning on the "Workflow customization" section when there are no notifications setup on a component for:

• Component was locked or unlocked
• Parse error occured
• New language was added or requested
• New alert emerged in a component
• Repository operation failed

This can also be accompanied by a list to the user's profile notification settings offering 'set this notifications' or something like that.

[nijel]

I think this makes sense, created #10654 as an issue for this.