dependabot: group docker actions updates

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

Author: thaJeztah

.github/dependabot.yml

@@ -14,6 +14,10 @@ updates:
       codeql-actions:
         patterns:
           - "github/codeql-action/*"
+      docker-actions:
+        patterns:
+          - "docker/*"
     labels:
       - "area/dependencies"
       - "bot"
+