refactor: move nixos-manual to reference/ + graphifyignore

reference/nixos-manual/configuration/profiles/graphical.section.md

@@ -0,0 +1,10 @@
+# Graphical {#sec-profile-graphical}
+
+Defines a NixOS configuration with the Plasma 6 desktop. It's used by the
+graphical installation CD.
+
+It sets [](#opt-services.xserver.enable),
+[](#opt-services.displayManager.sddm.enable),
+[](#opt-services.desktopManager.plasma6.enable),
+and [](#opt-services.libinput.enable) to true. It also
+includes glxinfo and firefox in the system packages list.