clanServices: Add missing manifest.readme to some services

clanServices/admin/README.md

@@ -0,0 +1,25 @@
+The admin service aggregates components that allow an administrator to log in to and manage the machine.
+
+The following configuration:
+
+1. Enables OpenSSH with root login and adds an SSH public key named`myusersKey` to the machine's authorized_keys via the `allowedKeys` setting.
+
+2. Automatically generates a password for the root user.
+
+```nix
+instances = {
+    admin = {
+        roles.default.tags = {
+            all = {  };
+        };
+        roles.default.settings = {
+            allowedKeys = {
+                myusersKey = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIEFDNnynMbFWatSFdANzbJ8iiEKL7+9ZpDaMLrWRQjyH lhebendanz@wintux";
+            };
+        };
+    };
+};
+```
+
+
+