Fix workflow for publishing to NPM (#1423)

Co-authored-by: Martin Henz <[email protected]>

.github/workflows/publish-npm.yml

@@ -1,23 +1,15 @@
 name: Publish to npm
 
 on:
-  pull_request:
+  push:
     branches:
       - master
-    types: [closed]
 
 jobs:
   verify:
     name: Verify should publish
     runs-on: ubuntu-latest
     steps:
-      - name: Verify PR merged
-        env:
-          IS_MERGED: ${{ github.event.pull_request.merged }}
-        run: |
-          if [ "$IS_MERGED" != "true" ]; then
-            echo "Pull request is not merged"; exit 1;
-          fi
       - name: Checkout repository
         uses: actions/checkout@v2
         with:
@@ -27,11 +19,16 @@ jobs:
         # We use jq as `npm pkg get version` returns a quoted string
         run: |
           if [ "$(cat package.json | jq -r .version)" == "$(npm view js-slang version)" ]; then
-            echo "Version has not changed"; exit 1;
+            echo "Version has not changed"
+            echo "UPDATE=false" >> "$GITHUB_OUTPUT"
+          else
+              echo "Version has changed";
+            echo "UPDATE=true" >> "$GITHUB_OUTPUT"
           fi
   publish:
     name: Publish to npm
     needs: [verify]
+    if: ${{ needs.verify.outputs.UPDATE == 'true' }}
     environment: publish-npm # Await approval from maintainers
     runs-on: ubuntu-latest
     steps: