ci/cd: add Continuous delivery workflow

.github/workflows/cd.docker.yml

@@ -0,0 +1,84 @@
+name: Continuous delivery
+
+on:
+  push:
+    branches: [ main ]
+    paths:
+      - '.github/workflows/cd.docker.yml'
+      - 'Dockerfile'
+
+  schedule:
+    - cron: 0 7 1 * * # at 07:00 on day-of-month 1, UTC
+
+  workflow_dispatch:
+    inputs:
+      reason:
+        description: The reason for dispatching it manually.
+        type: string
+        default: manual healthcheck
+        required: true
+
+concurrency:
+  group: packages
+  cancel-in-progress: true
+
+jobs:
+  publish:
+    name: Publishing
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      - name: Checkout the repository
+        uses: actions/checkout@v4
+        with: { fetch-depth: 0 }
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Login to GitHub Packages
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ github.token }}
+
+      - name: Define metadata for images
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: |
+            ghcr.io/lifeosm/whisper
+          tags: |
+            type=raw,value=latest
+      - name: Build and push images
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          file: Dockerfile
+          platforms: linux/amd64,linux/arm64
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          push: true
+
+  notify:
+    name: Notifying
+    needs: [ publish ]
+    runs-on: ubuntu-latest
+    if: failure() || success()
+
+    steps:
+      - name: Checkout the repository
+        uses: actions/checkout@v4
+        with: { fetch-depth: 0 }
+
+      - name: Send notification
+        uses: ./.github/actions/notify
+        continue-on-error: true
+        with:
+          emoji: 🐳
+          channel: ${{ secrets.SLACK_WEBHOOK }}
+          success: ${{ ! contains(needs.*.result, 'failure') }}