Add Docker Hub login and push steps to GitHub Actions workflow

.gitea/workflows/build.yml

@@ -14,3 +14,13 @@ jobs:
       - name: Build Docker image
         run: |
           docker build -t skoszewski/azure-cli:latest .
+
+      - name: Log in to Docker Hub
+        uses: docker/login-action@v3
+        with:
+          username: ${{ variables.DOCKER_HUB_USERNAME }}
+          password: ${{ secrets.DOCKER_HUB_ACCESS_TOKEN }}
+
+      - name: Push Docker image to Docker Hub
+        run: |
+          docker push skoszewski/azure-cli:latest