Add new workflow for building Docker image

This commit introduces a new GitHub Actions workflow used to build and push Docker images upon every push. This workflow uses Docker Buildx and automatically logs into the specified registry with stored credentials.

.gitea/workflows/build-image.yaml

@@ -0,0 +1,31 @@
+name: Build image and push it to registry
+
+on:
+  push
+
+
+jobs:
+  # Build job
+  build:
+    runs-on: cth-ubuntu-latest
+    steps:
+      - name: Check out repository
+        uses: https://github.com/actions/checkout@v4
+        
+      - name: Set up Docker Buildx
+        uses: https://github.com/docker/setup-buildx-action@v3
+
+      - name: Login to registry
+        uses: https://github.com/docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+          registry: 'h3m6q87t.gra7.container-registry.ovh.net'
+
+      - name: Build and push
+        uses: https://github.com/docker/build-push-action@v5
+        with:
+          context: ./pythonProject
+          file: ./pythonProject/Dockerfile
+          push: true
+          tags: 'h3m6q87t.gra7.container-registry.ovh.net/sign-pdf-worker/worker:latest'