chore: update env local example

.env.local.example

@@ -10,3 +10,6 @@ NEXT_PUBLIC_URL=
 
 # for docker, just set the domain to the container name, default is 'libremdb_redis'
 REDIS_URL=localhost:6379
+
+# if you want to use redis to speed up the media proxy, set this to true
+USE_REDIS = true