update drone config

.drone.yml

@@ -1,7 +1,7 @@
 kind: pipeline
 name: deploy
 steps:
-- name: docker 
+- name: docker
   image: plugins/docker
   settings:
     username:
@@ -11,4 +11,25 @@ steps:
     repo: aaronriedel/ansible-lint
     tags:
       - latest
-      - ${DRONE_COMMIT_SHA:0:8}
+      - ${DRONE_BUILD_NUMBER}
+  when:
+    branch:
+      - main
+- name: docker-build
+  image: plugins/docker
+  settings:
+    username:
+      from_secret: DOCKER_USERNAME
+    password:
+      from_secret: DOCKER_PASSWORD
+    repo: aaronriedel/ansible-lint
+    tags: latest
+    dry_run: true
+  when:
+    branch:
+      exclude:
+        - main
+when:
+  event:
+    include:
+      - push