refactor docker-release workflow to check package.json version more reliably

Author: HananoshikaYomaru

.github/workflows/docker-release.yml

@@ -19,8 +19,9 @@ jobs:
 
       - name: check if package.json version is updated by comparing with the previous commit
         run: |
-          git diff --name-only HEAD~1 HEAD | grep -q "package.json"
-          if [ $? -ne 0 ]; then
+          OLD_VERSION=$(git show HEAD~1:package.json | jq -r .version)
+          NEW_VERSION=$(jq -r .version package.json)
+          if [ "$OLD_VERSION" = "$NEW_VERSION" ]; then
             echo "Error: package.json version is not updated"
             exit 1
           fi