Add arch as supported os

Update `SUPPORTED_OS` to include the id `arch`. The install script supports `arch` but you can't proceed with a server install because `arch` isn't a `SUPPORTED_OS`

bootstrap/helpers/constants.php

@@ -40,6 +40,7 @@
     'ubuntu debian raspbian',
     'centos fedora rhel ol rocky amzn almalinux',
     'sles opensuse-leap opensuse-tumbleweed',
+    'arch',
 ];
 
 const SHARED_VARIABLE_TYPES = ['team', 'project', 'environment'];