fix: add permissionto workflow and enable run on push to master

.github/workflows/docker-publish-nptest.yml

@@ -1,6 +1,9 @@
 name: Build and Push Docker Image for network/benchmarks/netperf/nptest
 
 on:
+  push:
+    branches:
+      - master
   release:
     types: [published, edited]
 
@@ -28,5 +31,8 @@ jobs:
         make push
       env:
         DOCKERREPO: ghcr.io/${{ github.repository_owner }}/nptest
-        # IMAGE_TAG should be commit id if push else tag if release
-        IMAGE_TAG: ${{ github.event.release.tag_name }}
+        # IMAGE_TAG would be commit id if push else tag if release
+        IMAGE_TAG: ${{ github.event_name == 'push' && github.sha || github.event.release.tag_name }}
+
+permissions:
+  packages: write # Write permission is required to publish Docker images to GitHub Container Registry