Add ARM64 Builds (#15)

* Add ARM64 builds

* Move to a go-cron fork with arm64 support

* Use TARGETARCH directly in the script

* Use buildkit for docker build in readme

.github/workflows/build-and-push-images.yml

@@ -21,6 +21,12 @@ jobs:
       - name: Checkout repository
         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: Log in to DockerHub
         uses: docker/login-action@v1
         with:
@@ -35,3 +41,6 @@ jobs:
           tags: ${{ github.repository }}:${{ matrix.postgres }}
           build-args: |
             ALPINE_VERSION=${{ matrix.alpine }}
+          platforms: |
+            linux/amd64
+            linux/arm64