ci: add docker build action

.gitea/workflows/docker-build.yml

@@ -0,0 +1,36 @@
+name: Build and Push Docker Image
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  docker-build:
+    runs-on: docker
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v3
+
+      - name: Set up variables
+        run: |
+          IMAGE="${{ secrets.GITEA_REGISTRY }}/${{ secrets.GITEA_USERNAME }}/flingue-website"
+          SHA_TAG=$(echo "${GITHUB_SHA}" | cut -c1-7)
+          echo "IMAGE=$IMAGE" >> $GITHUB_ENV
+          echo "SHA_TAG=$SHA_TAG" >> $GITHUB_ENV
+
+      - name: Log in to Gitea Container Registry
+        run: |
+          echo "${{ secrets.REGISTRY_PASSWORD }}" | docker login \
+            -u "${{ secrets.REGISTRY_USERNAME }}" \
+            --password-stdin "${{ secrets.REGISTRY_URL }}"
+
+      - name: Build Docker image
+        run: |
+          docker build -t "$IMAGE:latest" -t "$IMAGE:${SHA_TAG}" .
+
+      - name: Push Docker image
+        run: |
+          docker push "$IMAGE:latest"
+          docker push "$IMAGE:${SHA_TAG}"
+