Allow overriding wg-quick and Homebrew prefix path

Notice: setting a different path for wg-quick or Homebrew prefix might result in a warning that WireGuard is not installed. This warning can be ignored.

Warning: setting a different path for wg-quick or Homebrew prefix that contains files or directories writable by non-root users will pose a serious risk as this allows a unprivileged user to gain full control of your system. Change these settings at your own risk!

To set a different path for the wg-quick binary run:

 sudo defaults write WireGuardStatusbarHelper wgquickBinPath /opt/local/bin/wg-quick

To set a different path for the Homebrew prefix run:

 sudo defaults write WireGuardStatusbarHelper brewPrefix /opt/local/