feat: include hostname while sending config event

hostname is autogenerated by librepages, config files, location in file
system, etc. are identified by hostname. So it makes sense to send
hostname, along with the custom domain names that the customer provides

env/libconductor/src/event_types.rs

@@ -30,6 +30,7 @@ pub enum EventType {
     },
 
     Config {
+        hostname: String,
         data: LibConfig,
     },
 }