Add instructions for excluding Pi-hole from Watchtower updates

Added instructions to exclude Pi-hole container from Watchtower's  auto-update system.

Signed-off-by: Alex Ferrarini <71784090+chippy01@users.noreply.github.com>

Author: chippy01

README.md

@@ -300,6 +300,20 @@ We have noticed that a lot of people use Watchtower to keep their Pi-hole contai
   - If you care about your data (logs/customizations), make sure you have it volume-mapped or it will be deleted in this step.
 - Recreate the container using the new image.
 
+If you wish to exclude the Pi-hole container from Watchtower's auto-update system you can update the Docker-compose in the following way:
+```yml
+services:
+  pihole:
+    container_name: pihole
+    image: pihole/pihole:latest
+    #---------------------------------------------------
+    # Rest of the previous Docker-compose configuration
+    #---------------------------------------------------
+    labels:
+          - "com.centurylinklabs.watchtower.enable=false"
+```
+This will result in Watchtower avoiding the update check on this container leaving it as it is without any interaction.
+
 Pi-hole is an integral part of your network, don't let it fall over because of an unattended update in the middle of the night.
 
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