Add new CI/CD workflow for 'update-starknet' branch

This commit introduces a new Continuous Integration/Continuous Deployment (CI/CD) workflow specifically for the 'update-starknet' branch. The workflow includes steps for setting up QEMU, Docker Buildx, and logging into DockerHub. Note that building and pushing Docker images is currently commented out.

.github/workflows/old-infra.yml

@@ -0,0 +1,28 @@
+name: ci
+
+on:
+  push:
+    branches:
+      - 'update-starknet'
+
+jobs:
+  docker:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Login to DockerHub
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v3
+        with:
+          push: true
+          tags: yukilabs/gol2-indexer:update-starknet