add linux builds

.github/workflows/build-push-linux.yml

@@ -0,0 +1,70 @@
+name: Build & Push Electron-Builder Linux Images
+
+on:
+  push:
+    branches: [ "main" ]
+    tags:
+      - "v*"
+  workflow_dispatch: {}
+
+env:
+  IMAGE_NAME: mrunknownde/electron-builder-linux
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - dockerfile: Dockerfile.node20-linux
+            short_tag: node20
+            latest: "true"
+          - dockerfile: Dockerfile.node18-linux
+            short_tag: node18
+            latest: "false"
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Login to Docker Hub
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+      - name: Docker meta
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.IMAGE_NAME }}
+          tags: |
+            type=raw,value=${{ matrix.short_tag }}
+            type=sha,format=long,prefix=${{ matrix.short_tag }}-
+          labels: |
+            org.opencontainers.image.title=electron-builder-linux
+            org.opencontainers.image.source=${{ github.repositoryUrl }}
+
+      - name: Build and push (multi-arch)
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: ./${{ matrix.dockerfile }}
+          # Linux-Build-Container kann gut multi-arch sein
+          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
+
+      - name: Also push :latest (only for Node 20)
+        if: ${{ matrix.latest == 'true' }}
+        run: |
+          docker buildx imagetools create \
+            --tag ${{ env.IMAGE_NAME }}:latest \
+            ${{ env.IMAGE_NAME }}:${{ matrix.short_tag }}