add varnish image build

.github/workflows/varnish.yml

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+name: Varnish image build
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+  schedule:
+    - cron: '24 9 * * 6'
+  workflow_dispatch:
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository }}
+  IMAGE_TAG: ${{ github.sha }}
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      - name: Checkout Dockerfile
+        id: checkout
+        uses: actions/checkout@v2
+
+      - name: Setup QEMU
+        id: qemu
+        uses: docker/setup-qemu-action@v1
+        with:
+          image: tonistiigi/binfmt:latest
+          platforms: all
+      
+      - name: Setup Docker Buildx
+        id: buildx
+        uses: docker/setup-buildx-action@v1
+
+      - name: Login to GitHub Container Registry
+        id: ghcr
+        uses: docker/login-action@v1
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.repository_owner }}
+          password: ${{ secrets.GH_TOKEN }}
+
+      - name: Extract metadata (tags, labels) for Docker
+        id: meta
+        uses: docker/metadata-action@v3
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          flavor: |
+            latest=${{ startsWith(github.ref, 'refs/heads/main') }}
+            suffix=-${{ github.sha }}
+
+      - name: Build and push Docker image
+        id: build
+        uses: docker/build-push-action@v2
+        with:
+          build-args: GH_TOKEN=${{ secrets.GH_TOKEN }}
+          context: .
+          file: ./varnish/Dockerfile
+          platforms: linux/amd64,linux/arm64/v8
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: varnish-${{ steps.meta.outputs.labels }}

varnish/Dockerfile

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+FROM varnish:fresh
+
+COPY default.vcl /etc/varnish/default.vcl

varnish/default.vcl

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+vcl 4.1;
+
+import dynamic;
+
+backend default none;
+
+sub vcl_init {
+    new backend = director(port = "8000");
+}
+
+sub vcl_recv {
+    set req.http.host = "revanced-releases-api";
+    set req.backend_hint = backend.backend("revanced-releases-api");
+}