[Brigadier] Common issues + FAQ

[!NOTE]
This issue is part of a series of issues regarding the extension of the Paper documentation regarding Paper's Brigadier API.

I think it would be really useful to have a FAQ/Common issues page that we can just link to people if they run into standard issues or have frequently asked questions.

Some of the FAQ points could include:

• "Can I declare commands using annotations?"
• "What is the earliest version I can use Brigadier at?"
• "How can I display a client-side error for my custom arguments?"

More can be taken from the Discord server #paper-dev channel. This definitely does not cover all of them

Some of the common issues points could include:

• Misplaced brackets deforming the command tree

Similar to the FAQ, I just couldn't think of more in this short time. The #paper-dev channel can be used as a reference + you can suggest some here on this issue

Furthermore, I think a section about community-driven command frameworks could be useful. The Brigadier API was mainly exposed so that command frameworks have an easier time doing their stuff, so I think it is just fair to refer to some of them.

No file or test is named in the issue. Start by reviewing the existing Paper Brigadier documentation and the #paper-dev channel for recurring questions and common issues; the work is done when a FAQ/common-issues page covers the proposed topics and references relevant community-driven command frameworks.