Add docker build workflow

.github/workflows/docker.yaml

@@ -0,0 +1,34 @@
+name: Build Docker Image
+
+on:
+  push:
+    branches:
+      - main
+
+permissions:
+  packages: write
+
+jobs:
+  docker:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Log in to Gitea Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: gitea.lol3r.com
+          username: leon
+          password: ${{ secrets.DOCKER_PAT }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: ./Dockerfile
+          push: true
+          tags: |
+            gitea.lol3r.com/leon/blog:latest
+            gitea.lol3r.com/leon/blog:${{ gitea.sha }}