add link_checker

.github/workflows/link_checker.yml

@@ -0,0 +1,21 @@
+name: Check Docs links
+
+on:
+  push:
+  pull_request:
+  schedule:
+    # Run everyday at 3 am UTC 
+    - cron: 0 3 * * *
+
+jobs:
+  markdown-link-check:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout
+      uses: actions/checkout@master
+    - name: Run link check
+      uses: gaurav-nelson/github-action-markdown-link-check@v1
+      with:
+        use-quiet-mode: 'yes'
+        use-verbose-mode: 'yes'
+        file-extension: '.rst, .md'