docs: skipping of setup mode

This PR documents functionality added by
https://github.com/freifunk-gluon/packages/pull/95

docs/site-example/site.conf

@@ -146,6 +146,11 @@
     },
   },
 
+  -- Skip setup mode (config mode) on first boot
+  -- setup_mode = {
+  --  skip = true,
+  -- },
+
   -- These strings are shown in config mode. Some HTML is permissible.
   --
   -- msg_welcome: shown at startup

docs/user/site.rst

@@ -150,6 +150,15 @@ simple_tc : package
         },
       },
 
+setup_mode : package
+    Allows skipping setup mode (config mode) at first boot when attribute
+    ``skip`` is set to ``true``. This is optional and may be left out.
+    ::
+
+      setup_mode {
+        skip = true,
+      },
+
 config_mode : package
     Configuration Mode text blocks