🐳 Add automatic nightly docker build of master

.github/workflows/docker-images-nightly.yml

@@ -0,0 +1,38 @@
+name: Docker Nightly Image CI
+
+on:
+  schedule:
+    - cron: "0 2 * * *"
+  workflow_dispatch:
+
+jobs:
+
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+      -
+        name: Checkout
+        uses: actions/checkout@v2
+      -
+        name: Set up QEMU
+        uses: docker/setup-qemu-action@v1
+      -
+        name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+      -
+        name: Login to DockerHub
+        uses: docker/login-action@v1
+        with:
+          username: ${{ secrets.DOCKER_USERNAME }}
+          password: ${{ secrets.DOCKER_PASSWORD }}
+      -
+        name: Build and push
+        uses: docker/build-push-action@v2
+        with:
+          context: .
+          file: ./docker/images/n8n-custom/Dockerfile
+          platforms: linux/amd64
+          push: true
+          tags: n8nio/n8n:nightly