Fix to require docker-push on version bump #79 (#80)

Author: astrochun

.github/workflows/docker.yml

@@ -23,7 +23,7 @@ jobs:
   # Push Docker images
   docker-push:
     runs-on: ubuntu-latest
-    if: contains(github.ref, 'refs/tags')
+    if: contains(github.ref, 'refs/tags/v')
     steps:
     - name: Checkout
       uses: actions/checkout@v2