send email on merge failure

.github/workflows/merge-upstream-master.yml

@@ -41,3 +41,22 @@ jobs:
     # Step 4: Print a helpful timestamp for your records (not required, just nice)
     - name: Timestamp
       run: date
+
+    - name: Send email
+      if: failure()
+      uses: dawidd6/action-send-mail@v3.2.0
+      with:
+          # mail server settings
+          server_address: smtp.gmail.com
+          server_port: 465
+          # user credentials
+          username: ${{ secrets.EMAIL }}
+          password: ${{ secrets.EMAIL_PASSWORD }}
+          # email subject
+          subject: ${{ github.job }} job of ${{ github.repository }} has ${{ job.status }}
+          # email body as text
+          body: ${{ github.job }} job in worflow ${{ github.workflow }} of ${{ github.repository }} has ${{ job.status }}
+          # comma-separated string, send email to
+          to:  ${{ secrets.EMAIL }}
+          # from email name
+          from: Github Action