CI: Add workflow to check for broken links

Spot any broken links from TSC minutes. Some links can be
crucial for referecing importan information that needs to be
revisited.

This workflow can be modified to enable "check-modified-files-only"
if the team decides to ignore the current broken links.

Signed-off-by: Jessica Wagantall <[email protected]>

.github/workflows/check-links.yml

@@ -0,0 +1,15 @@
+name: Check Markdown links
+
+on:
+  pull_request:
+    paths:
+      - '**/*.md'
+
+jobs:
+  check-links:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@master
+    - uses: gaurav-nelson/github-action-markdown-link-check@v1
+      with:
+        use-quiet-mode: 'yes'