Disable Hadolint rules

Skip Hadolint rule DL3018 (DL3018 warning: Pin versions in apk add)
because Alpine does not keep older package versions which will cause
builds to break when packages are updated.

Skip Hadolint rule DL3003 (Use WORKDIR to switch to a directory) as
breaking up the main 'RUN apk add' statement would create more layers in
the build.

.github/workflows/lint.yml

@@ -33,6 +33,7 @@ jobs:
         with:
           dockerfile: 1.1.21.2/Dockerfile
           failure-threshold: warning
+          ignore: DL3018,DL3003
 
   checkov:
     name: Run Checkov for Dockerfile Security Analysis