ci: 👷 add Drone Docker build

.drone.yml

@@ -0,0 +1,25 @@
+kind: pipeline
+type: kubernetes
+name: Build Docker image on main
+
+steps:
+  - name: build image
+    image: plugins/docker
+    settings:
+      repo: gitea.ravianand.me/dan6erbond/listy
+      registry: gitea.ravianand.me
+      username:
+        from_secret: docker_username
+      password:
+        from_secret: docker_password
+      tags:
+        - main
+        - latest
+
+trigger:
+  branch:
+    - main
+  event:
+    include:
+      - push
+      - custom