[arch-general] Documentation about pambase

It's nice that Arch introduced the pambase package, so that there's some referent point of pam configuration. But currently it lacks any documentation and recommendations how those files should be used (for people that it's not so obvious). Especially something we can point to people making packages on AUR. For ex. what should lightdm use? just include /etc/pam.d/system-login or /etc/pam.d/system-local-login? -- дамјан