fix(buster): make buster a gloabl command

Yarn's cache is relative to the user, and has no requirement on any ghost instance.

Author: vikaspotluri123

lib/commands/buster.js

@@ -11,5 +11,6 @@ class BusterCommand extends Command {
 
 BusterCommand.description = 'Who ya gonna call?';
 BusterCommand.longDescription = 'When there\'s something strange in your neighborhood....';
+BusterCommand.global = true;
 
 module.exports = BusterCommand;