Mod shouts in text channels

As stated in the title, I suggest adding the ability to label a message as an "Official Mod Shout". Official mod shouts should be highlighted.

Why would it be useful ?

- Users are more likely to listen to official messages than normal ones.

- Mods could clearly state if they send a message as a mod, or as a normal human.

- It would accuentuate official mod shouts, so they don't get ignored

(for example, Reddit has already a similar feature called "distinguish as mod")