chore: add Docker login in test jobs to increase DockerHub rate limit

Author: le0m

.github/workflows/main.yml

@@ -42,6 +42,12 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
 
+      - name: Login to DockerHub
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKER_USERNAME }}
+          password: ${{ secrets.DOCKER_PASSWORD }}
+
       - name: Build image for testing
         uses: docker/build-push-action@v5
         with: