ci: perform hadolint check in deploy pipeline

...a failsafe of sorts

.drone.yml

@@ -193,11 +193,20 @@ steps:
     commands:
       - rm -rf ./public
 
+  - name: hadolint
+    image: hadolint/hadolint:v2.9.1-alpine
+    depends_on:
+      - clone
+    commands:
+      - hadolint --version
+      - hadolint Dockerfile
+
   - name: build
     pull: always
     image: tmaier/docker-compose:latest
     depends_on:
       - rm-intermediate
+      - hadolint
     volumes:
       - name: s
         path: /var/run/docker.sock