Update to Watcher 6

Improve upload performance by relying on the file watcher instead of
synchronously creating thumbnails before responding to the client.

Cargo.toml

@@ -27,9 +27,9 @@ chrono = "0.4"
 dotenv = "0.15"
 bcrypt = "0.9"
 image = { version = "0.23", default-features = false, features = ["jpeg", "png", "jpeg_rayon"] }
-walkdir = "2"
+walkdir = "2.4.0"
 rayon = "1.5"
-notify = "4.0"
+notify = "6.1.1"
 path-absolutize = "3.0"
 log="0.4"
 env_logger="0.8"