docs: add part about default annotation

Signed-off-by: deggja <[email protected]>

README.md

@@ -37,6 +37,8 @@ Reloader is compatible with Kubernetes >= 1.19
 
 You have a `Deployment` called `foo` and a `ConfigMap` and/or a `Secret` either mounted as a volume or defined as a environment variable. The `ConfigMap` and `Secret` can be named whatever, but for the sake of this example, lets refer to the `ConfigMap` as `foo-configmap` and the secret as `foo-secret`.
 
+Add the annotation to the main metadata of your `Deployment`. By default this would be `reloader.stakater.com/auto`.
+
 ```yaml
 kind: Deployment
 metadata: