Added a workflow to publish to pub.dev

.github/workflows/publish-on-merge.yml

@@ -0,0 +1,12 @@
+name: Publish to pub.dev
+'on':
+  push:
+    branches:
+      - master
+  workflow_dispatch: # Run workflow manually (without waiting for the cron to be called), through the Github Actions Workflow page directly
+
+jobs:
+  publish:
+    permissions:
+      id-token: write # Required for authentication using OIDC
+    uses: dart-lang/setup-dart/.github/workflows/publish.yml@v1