Add Docker build configuration.

.drone.yml

@@ -0,0 +1,24 @@
+kind: pipeline
+name: documentation
+
+clone:
+  skip_verify: true
+
+steps:
+- name: build
+  image: plugins/docker
+  settings:
+    username:
+      from_secret: docker_username
+    password:
+      from_secret: docker_password
+    registry: projects.torsion.org
+    repo: projects.torsion.org/witten/mediagoblin-docker
+
+trigger:
+  repo:
+    - witten/mediagoblin-docker
+  branch:
+    - master
+  event:
+    - push