add custom index

sample.conf

@@ -17,4 +17,10 @@ ttl = "180"
 no_cache = '.*(?:db|db\.sig)$'
 
 # Redirect only paths matching this regex to the mirrors, return 404 otherwise
-only_allow = '^\/archlinux'
+only_allow = '^\/archlinux'
+
+# Show an index page on root path /
+# Options:
+# - `no` // disable index page
+# - `<path>` // custom index page html file
+index = "no"