Update Notes.md. Added comments for workflow example

Author: Chau-Nguyen-Developer

Notes.md

@@ -1,4 +1,31 @@
 ## Notes
 * Workflows have jobs, and jobs have steps.  
 * Each step consists of either a shell script that is executed, or a reference to an action that is run. When we talk about an action in this context, we mean a reusable unit of code.   
-* An action is a pre-defined, reusable set of jobs or code that perform specific tasks within a workflow.  
+* An action is a pre-defined, reusable set of jobs or code that perform specific tasks within a workflow.
+
+### Example of workflow
+_//The name of this workflow_  
+name: Post welcome comment  
+_//Trigger this workflow only when a PR is opened (not edited or closed)_  
+on:  
+  pull_request:  
+    types: [opened]  
+  _//The workflow needs write permissions to comment on pull requests._  
+  permissions:  
+    pull-requests: write  
+  _//Define a job called "build". The name could be anything. It is just a label._    
+  jobs:  
+    build:  
+      name: Post welcome comment  
+      _//The runner (virtual machine) will be Ubuntu Linux._  
+      runs-on: ubuntu-latest  
+     _//The steps inside the job._  
+      steps:  
+        _//This step runs a command that posts a comment saying "Welcome to the repository!"_  
+        - run: gh pr comment $PR_URL --body "Welcome to the repository!"  
+          _//The below setting sets environment variables_  
+          env:  
+            _//A token that allows the GitHub CLI to authenticate_  
+            GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}  
+            _//The URL of the pull request that triggered the event._  
+            PR_URL: ${{ github.event.pull_request.html_url }}