add drone auto build

.drone.yml

@@ -0,0 +1,28 @@
+---
+kind: pipeline
+type: default
+
+steps:
+- name: build
+  image: golang:alpine
+  commands:
+  - CGO_ENABLED=0 GOOS=linux go build -a -o drone-dingtalk-message .
+  - ./drone-dingtalk-message
+- name: publish
+  image: plugins/docker
+  when:
+    branch:
+    - beta
+    status:
+    - success
+    event:
+    - push
+  settings:
+    repo: lddsb/drone-dingtalk-message
+    dockerfile: Dockerfile
+    tags: beta
+    username:
+      from_secret: docker_username
+    password:
+      from_secret: docker_password
+