hadolint: ignore DL3003 (Use WORKDIR to switch to a directory)

.hadolint.yaml

 ignored:
   # For more information, see https://github.com/hadolint/hadolint/wiki/$RULE
+  # Use WORKDIR to switch to a directory
+  - DL3003
   # Do not use apt-get upgrade or dist-upgrade
   - DL3005
   # Pin versions in apt-get install