Fix Docker promote (#25)

Author: goruha

.github/workflows/docker-promote.yml

@@ -17,6 +17,10 @@ jobs:
   ci-docker:
     runs-on: ubuntu-latest
     steps:
+      - name: Set output
+        id: vars
+        run: echo "tag=${GITHUB_REF#refs/*/}" >> $GITHUB_OUTPUT
+    
       - uses: cloudposse/github-action-docker-promote@0.3.0
         id: promote
         with:
@@ -27,5 +31,5 @@ jobs:
           password: "${{ secrets.GITHUB_TOKEN }}"
           platforms: linux/amd64,linux/arm64
           from: sha-${{ github.sha }}
-          to: ${{ github.event.release.tag_name }}
-          use_metadata: false
+          to: ${{ steps.vars.outputs.tag }}
+          use_metadata: false