Add publishing workflow

.github/workflows/publish.yml

@@ -0,0 +1,44 @@
+on:
+  workflow_dispatch:
+    inputs:
+      container_tag:
+        description: Tag for container
+        default: "latest"
+        required: true
+
+  push:
+    branches:
+      - main
+
+  schedule:
+    - cron: '0 0 12 1/1 *'
+
+name: Publish container
+
+env:
+  CONTAINER_NAME: jordemort/pleroma:${{ github.event.inputs.container_tag || 'latest' }}
+  DOCKER_CLI_EXPERIMENTAL: enabled
+
+jobs:
+  publish:
+    name: Build and publish image
+    runs-on: ubuntu-20.04
+
+    steps:
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v1
+
+      - name: Set up Docker Buildx
+        id: buildx
+        uses: docker/setup-buildx-action@v1
+
+      - name: Login to container registry
+        uses: docker/login-action@v1
+        with:
+          username: ${{ secrets.REGISTRY_USERNAME }}
+          password: ${{ secrets.REGISTRY_TOKEN }}
+
+      - uses: actions/checkout@v2
+
+      - name: Build and push container
+        run: docker buildx build --push --pull --platform "linux/amd64,linux/arm64,linux/arm/v7" --cache-from "$CONTAINER_NAME" --tag "$CONTAINER_NAME" .