ci: add workflow to build and publish container image on GHCR

.github/workflows/build-container-image.yml

@@ -0,0 +1,43 @@
+name: Build container image
+
+on:
+  push:
+    branches: [main]
+    tags: ["v*"]
+
+permissions:
+  contents: read
+  packages: write
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v5
+
+      - uses: docker/setup-buildx-action@v3
+
+      - uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ghcr.io/${{ github.repository }}
+          tags: |
+            type=ref,event=branch
+            type=semver,pattern={{version}}
+            type=sha
+
+      - uses: docker/build-push-action@v6
+        with:
+          context: .
+          platforms: linux/amd64,linux/arm64
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max

Dockerfile

@@ -1,5 +1,5 @@
 # Build the manager binary
-FROM golang:1.26 AS builder
+FROM --platform=$BUILDPLATFORM golang:1.26 AS builder
 ARG TARGETOS
 ARG TARGETARCH