Add Daily Link Check GitHub Workflow (PowerShell#17351)

* add github workflow for daily link checking

* remove extra name statement

* increase indentation

* scan all files, not just modified ones

* add retries for 429 errors

* increase timeout for status 0 errors

* uncomment teams notifier task

* fix experimental features link

* add copyright header

* Update .github/workflows/markdownLinkDaily.yml

Co-authored-by: Travis Plunk <travis.plunk@microsoft.com>

Author: tgauth

.github/PULL_REQUEST_TEMPLATE.md

@@ -19,7 +19,7 @@
 - **[Breaking changes](https://github.com/PowerShell/PowerShell/blob/master/.github/CONTRIBUTING.md#making-breaking-changes)**
     - [ ] None
     - **OR**
-    - [ ] [Experimental feature(s) needed](https://github.com/MicrosoftDocs/PowerShell-Docs/blob/staging/reference/6/Microsoft.PowerShell.Core/About/about_Experimental_Features.md)
+    - [ ] [Experimental feature(s) needed](https://github.com/MicrosoftDocs/PowerShell-Docs/blob/main/reference/7.3/Microsoft.PowerShell.Core/About/about_Experimental_Features.md)
         - [ ] Experimental feature name(s): <!-- Experimental feature name(s) here -->
 - **User-facing changes**
     - [ ] Not Applicable

.github/workflows/markdown-link/config.json

@@ -1,3 +1,7 @@
 {
+  "timeout": "40s",
+  "retryOn429": true,
+  "retryCount": 5,
+  "fallbackRetryDelay": "30s",
   "aliveStatusCodes": [504, 503, 403, 200]
 }

.github/workflows/markdownLinkDaily.yml

@@ -0,0 +1,29 @@
+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT license.
+
+name: PowerShell Daily Markdown Link Verification
+
+on:
+  workflow_dispatch:
+  schedule:
+  # At 13:00 UTC every day.
+  - cron:  '0 13 * * *'
+
+jobs:
+  markdown-link-check:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout
+      uses: actions/checkout@master
+    - name: Check Links
+      uses: gaurav-nelson/github-action-markdown-link-check@v1
+      with:
+        use-quiet-mode: 'yes'
+        use-verbose-mode: 'yes'
+        config-file: .github/workflows/markdown-link/config.json
+    - name: Microsoft Teams Notifier
+      uses: skitionek/notify-microsoft-teams@master
+      if: failure()
+      with:
+        webhook_url: ${{ secrets.PS_BUILD_TEAMS_CHANNEL }}
+        overwrite: "{title: `Failure in .github/markdownLinkDaily.yml validating links. Look at ${workflow_link}`}"