ci: Run Hadolint on Dockerfiles

Run the Hadolint Dockerfile linter.

.github/workflows/ci.yml

@@ -27,6 +27,20 @@ jobs:
     - name: "Check out NIPAP repository"
       uses: actions/checkout@v2
 
+    - name: "Hadolint nipapd"
+      uses: hadolint/[email protected]
+      with:
+        Dockerfile: Dockerfile.nipapd
+        override-info: "DL3008, DL4000"
+        failure-threshold: error
+
+    - name: "Hadolint WWW"
+      uses: hadolint/[email protected]
+      with:
+        Dockerfile: Dockerfile.www
+        override-info: "DL3008, DL4000"
+        failure-threshold: error
+
     - name: "Install dependencies and prepare NIPAP"
       run: |
         # Set up NIPAP repo