ci: add github actions docker build

.github/workflows/docker.yml

@@ -0,0 +1,52 @@
+name: Build and publish a Docker image to Docker hub and ghcr.io
+on:
+    push:
+        branches:
+            - master
+        tags:
+            - 'v*.*.*'
+
+jobs:
+    docker:
+        runs-on: ubuntu-latest
+        steps:
+            - name: Checkout
+              uses: actions/checkout@v2
+            - name: Docker meta
+              id: meta
+              uses: docker/metadata-action@v3
+              with:
+                  # list of Docker images to use as base name for tags
+                  images: |
+                      nodemailer/wildduck
+                      ghcr.io/nodemailer/wildduck
+                  # generate Docker tags based on the following events/attributes
+                  tags: |
+                      type=semver,pattern={{version}}
+                      type=semver,pattern={{major}}.{{minor}}
+                      type=semver,pattern={{major}}
+                      type=sha
+            - 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
+              if: github.event_name != 'pull_request'
+              uses: docker/login-action@v1
+              with:
+                  username: ${{ secrets.DOCKERHUB_USERNAME }}
+                  password: ${{ secrets.DOCKERHUB_TOKEN }}
+            - name: Login to GHCR
+              if: github.event_name != 'pull_request'
+              uses: docker/login-action@v1
+              with:
+                  registry: ghcr.io
+                  username: ${{ github.repository_owner }}
+                  password: ${{ secrets.GITHUB_TOKEN }}
+            - name: Build and push
+              uses: docker/build-push-action@v2
+              with:
+                  context: .
+                  push: ${{ github.event_name != 'pull_request' }}
+                  tags: ${{ steps.meta.outputs.tags }}
+                  labels: ${{ steps.meta.outputs.labels }}