first go at creating the build action

.github/workflows/docker.yml

@@ -0,0 +1,51 @@
+name: Build and Publish Docker Images
+on:
+  push:
+
+jobs:
+  buildmatrix:
+    name: Create Build Matrix
+    runs-on: ubuntu-latest
+    outputs:
+      matrix: ${{ steps.set-matrix.outputs.matrix }}
+    steps:
+      - name: Set up matrix
+        id: set-matrix
+        run: |
+          echo "matrix=$(curl https://download.dokuwiki.org/version | jq -c 'del(.master) | {release: [.[]]}')" >> $GITHUB_OUTPUT
+
+  build:
+    needs: buildmatrix
+    name: Build Docker Image ${{ matrix.release.date }}
+    runs-on: ubuntu-latest
+    strategy:
+      matrix: ${{fromJson(needs.buildmatrix.outputs.matrix)}}
+    steps:
+      -
+        name: Checkout
+        uses: actions/checkout@v2
+      -
+        name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+      -
+        name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+      -
+        name: Login to DockerHub
+        uses: docker/login-action@v3
+        with:
+          username: splitbrain
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+      -
+        name: Build and push
+        uses: docker/build-push-action@v5
+        with:
+          platforms: linux/amd64,linux/arm64
+          push: true
+          cache-from: type=gha, scope=${{ github.workflow }}
+          cache-to: type=gha, scope=${{ github.workflow }}
+          tags: |
+            dokuwiki/dokuwiki:${{ matrix.release.date }}
+            dokuwiki/dokuwiki:${{ matrix.release.type }}
+          build-args: |
+             DOKUWIKI_VERSION=${{ matrix.release.date }}