improve readme

ffmuc-custom-banner/README.md

@@ -2,16 +2,18 @@
 
 This package modifies the /etc/banner that is shown during SSH login.
 
+The custom banner template is located [here](files/etc/banner.gluon).
+
 ⚠️ This package will consume an additional 2x the banner size, one for the template and one for the final banner. Make sure to have enough flash size available.
 
 
 ### Configuration
 
-You should use something like the following in the site.conf:
+The custom banner can optionally also be configured in the site.conf:
 
 ```lua
 custom_banner = {
-    enabled = true,
-    map_url = 'https://map.ffmuc.net/#!/',
-    },
+    enabled = true,                        -- optional (enabled by default)
+    map_url = 'https://map.ffmuc.net/#!/', -- optional (skipped by default)
+},
 ```