Support SSH to IPv6 EC2 instance for Turms playground

.github/workflows/deploy-playground.yml

@@ -21,12 +21,20 @@ jobs:
     if: ${{ !github.event.workflow_run || github.event.workflow_run.conclusion == 'success' }}
     runs-on: ubuntu-22.04
     steps:
+      - name: Set up WARP
+        uses: fscarmen/[email protected]
+        with:
+          stack: dual
+
       - name: SSH
-        uses: appleboy/[email protected]
+        # FIXME: Use the "master" branch as a workaround because
+        # ssh-action hasn't released a new version that supports IPv6.
+        uses: appleboy/ssh-action@master
         with:
           host: ${{ secrets.PLAYGROUND_SSH_HOST }}
           username: ${{ secrets.PLAYGROUND_SSH_USERNAME }}
           key: ${{ secrets.PLAYGROUND_SSH_KEY }}
+          protocol: tcp6
           script_stop: true
           script: |
             cd /opt/turms