Allow `-` in the command

[xt0rted]

The regex being used matches a-zA-Z0-9_. Updating this to include - will let you match usernames which can't be done currently. Usernames have the following criteria:

• Must start with a-zA-Z0-9
• Can contain multiple - but not consecutively
• Must end with a-zA-Z0-9

This is the current regex:

/^\/([\w]+)\b *(.*)?$/m

And this is what I'm thinking of switching to:

/^\/([a-zA-Z0-9]+(?:[-_][a-zA-Z0-9]+)*) *(.*)?$/m