[docker] Add CI to build and archive docker image

.github/workflows/build.yml

@@ -308,3 +308,16 @@ jobs:
       with:
         name: idevicerestore-latest_${{ matrix.arch }}-${{ env.dest }}
         path: idevicerestore.tar
+  build-docker:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: build
+        run: |
+          pushd docker && ./build.sh; popd
+          docker image save -o idevicerestore-docker.tar idevicerestore-docker
+      - name: publish artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: idevicerestore-latest_docker
+          path: idevicerestore-docker.tar