Add base webpack testing

.drone.yml

@@ -0,0 +1,19 @@
+kind: pipeline
+name: webpack
+
+steps:
+  - name: build
+    image: nextcloudci/node:node-4
+    commands:
+      - npm ci
+      - npm run build
+  - name: changes
+    image: nextcloudci/node:node-4
+    commands:
+      - git status
+      - bash -c "[[ ! \"`git status --porcelain `\" ]] || ( echo 'Uncommited changes in webpack build' && exit 1 )"
+
+trigger:
+  branch:
+    - master
+    - stable*