add docker workflow

.github/workflows/docker.yml

@@ -0,0 +1,66 @@
+name: Docker
+
+on:
+  push:
+    branches:
+      - main
+    tags:
+      - 'v*'
+
+
+jobs:
+  Build-and-Push:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Prepare Docker Meta
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: |
+            ghcr.io/transprogrammer/rodhaj
+          tags: |
+            type=semver,pattern={{version}}
+            type=semver,pattern={{major}}.{{minor}}
+            type=semver,pattern={{major}}
+            type=edge,branch=main
+
+      - name: Setup Docker Buildx
+        id: buildx
+        uses: docker/setup-buildx-action@v3
+        with:
+          version: latest
+
+      - name: Login to GitHub Container Registry
+        uses: docker/login-action@v3
+        # Skip when PR from a fork
+        if: ${{ !github.event.pull_request.head.repo.fork }}
+        with:
+          registry: ghcr.io
+          username: ${{ github.repository_owner }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+
+      - name: Determine build cache output
+        id: cache-target
+        run: |
+          if [[ "${{ github.event_name }}" == "pull_request" ]]; then
+            # Essentially just ignore the cache output (PR can't write to registry cache)
+            echo "cache-to=type=local,dest=/tmp/discard,ignore-error=true" >> $GITHUB_OUTPUT
+          else
+            echo "cache-to=type=registry,mode=max,ref=ghcr.io/${{ github.repository_owner }}/rodhaj:bot" >> $GITHUB_OUTPUT
+          fi
+
+      - name: Build and push image
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: ./docker/Dockerfile
+          # Skip pushing when PR from a fork
+          push: ${{ !github.event.pull_request.head.repo.fork }}
+          cache-from: type=registry,ref=ghcr.io/${{ github.repository_owner }}/rodhaj:bot
+          cache-to: ${{ steps.cache-target.outputs.cache-to }}
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}