added drone config

.drone.jsonnet

@@ -0,0 +1,22 @@
+[
+  {
+    kind: 'pipeline',
+    type: 'docker',
+    name: 'docker-build',
+    steps: [
+      {
+        name: 'build-fvtt',
+        image: 'plugins/docker',
+        settings: {
+          tags: ['latest', '${DRONE_COMMIT_SHA:0:8}'],
+          dockerfile: 'Dockerfile',
+          auto_tag: true,
+          registry: 'registry.d1v3.de',
+          repo: 'registry.d1v3.de/cacheserver',
+          config: { from_secret: 'dockerconfigjson' },
+        },
+      },
+    ],
+    trigger: { event: ['push'] },
+  },
+]