Add --help (or @help) for commands

Currently, commands like "/gamemode doInsomnia" have no explanation for what they do. In a regular terminal, running something like "sudo --help" would tell you:

sudo - execute a command as another user 
 
usage: sudo -h | -K | -k | -V 
usage: sudo -v [-ABkNnS] [-g group] [-h host] [-p prompt] [-u user] 
usage: sudo -l [-ABkNnS] [-g group] [-h host] [-p prompt] [-U user] 
            [-u user] [command [arg ...]] 
usage: sudo [-ABbEHkNnPS] [-r role] [-t type] [-C num] [-D directory] 
            [-g group] [-h host] [-p prompt] [-R directory] [-T timeout] 
            [-u user] [VAR=value] [-i | -s] [command [arg ...]] 
usage: sudo -e [-ABkNnS] [-r role] [-t type] [-C num] [-D directory] 
            [-g group] [-h host] [-p prompt] [-R directory] [-T timeout] 
            [-u user] file ... 
 
Options: 
  -A, --askpass                 use a helper program for password prompting 
  -b, --background              run command in the background 
...

What the command does is explained, as well as what different options do. I have no idea if "--help" is a valid player name, but if it is then "@help" would also work.