Improve consistency of chat command user-facing data

[budak7273]

• Chat command helptext is currently exactly what the developer writes
• Standards for optional vs required arguments (possible to enforce?) ex. [optional] <required> (required)
• Fallback for if no helptext is written
• Communicate aliases somehow

Developer experience:

• Fix No error message produced when 2 chat commands are registered with the same CommandName #397
• Hidden commands? (For deprecating an old command name)

https://discord.com/channels/555424930502541343/562722670974599227/1445441754475135006