Lint Dockerfile files with Hadolint

.docker/validate-against-schema/Dockerfile

@@ -1,3 +1,3 @@
-FROM alpine:3.11.3
+FROM alpine:3.17.3
 
-RUN apk add --no-cache libxml2-utils
+RUN apk add --no-cache libxml2-utils=2.10.4-r0

.github/workflows/ci-dockerfile.yml

@@ -0,0 +1,28 @@
+# https://help.github.com/en/categories/automating-your-workflow-with-github-actions
+
+name: "Continuous Integration for Dockerfile files"
+
+on:
+  pull_request:
+    paths:
+      - ".docker/**/*"
+  push:
+    branches:
+      - "*.*.x"
+    paths:
+      - ".docker/**/*"
+  schedule:
+    - cron: "0 17 * * *"
+
+jobs:
+  lint-dockerfile:
+    name: "Lint Dockerfile files with Hadolint"
+    runs-on: "ubuntu-22.04"
+
+    steps:
+      - uses: "actions/checkout@v3"
+
+      - name: "Lint Dockerfile"
+        uses: "hadolint/hadolint-action@v3.1.0"
+        with:
+          dockerfile: ".docker/validate-against-schema/Dockerfile"