Add markdown-toc to CI checks (#2023)

* Add markdown-toc to tooling

* Remove special characters from markdown toc

* Add markdown-toc CI check

* Remove sudo from markdown-toc CI check

* Fix merge issue

.github/workflows/checks.yaml

@@ -45,6 +45,21 @@ jobs:
     - name: run markdown-link-check
       run: make markdown-link-check
 
+  markdown-toc-check:
+    runs-on: ubuntu-latest
+    steps:
+    - name: check out code
+      uses: actions/checkout@v2
+
+    - name: install markdown-toc
+      run: make install-markdown-toc
+
+    - name: run markdown-toc
+      run: make markdown-toc
+
+    - name: validate markdown-toc
+      run: git diff --exit-code ':*.md' || (echo 'Generated markdown Table of Contents is out of date, please run "make markdown-toc" and commit the changes in this PR.' && exit 1)
+
   misspell:
     runs-on: ubuntu-latest
     steps: