refactor: move nixos-manual to reference/ + graphifyignore

reference/nixos-manual/configuration/ssh.section.md

@@ -0,0 +1,20 @@
+# Secure Shell Access {#sec-ssh}
+
+Secure shell (SSH) access to your machine can be enabled by setting:
+
+```nix
+{ services.openssh.enable = true; }
+```
+
+By default, root logins using a password are disallowed. They can be
+disabled entirely by setting
+[](#opt-services.openssh.settings.PermitRootLogin) to `"no"`.
+
+You can declaratively specify authorised public keys for a user
+as follows:
+
+```nix
+{
+  users.users.alice.openssh.authorizedKeys.keys = [ "ssh-ed25519 AAAAB3NzaC1kc3MAAACBAPIkGWVEt4..." ];
+}
+```