plugin/reload: mention auto in reload
mention auto in reload docs
## Description
+This plugin allows automatic reload of a changed _Corefile_.
+To enable automatic reloading of _zone file_ changes, use the `auto` plugin.
+
This plugin periodically checks if the Corefile has changed by reading
it and calculating its MD5 checksum. If the file has changed, it reloads
CoreDNS with the new Corefile. This eliminates the need to send a SIGHUP
