Merge #4775

4775: Markdown links CI check r=newhoggy a=newhoggy

This adds a CI check to make sure Markdown links are valid.

There are currently failures in this CI check, but the idea is to merge the PR as is and then ask the respective teams to fix the invalid links.

Depends on:
* input-output-hk/cicero#67
*  IntersectMBO/cardano-ledger#3245
* input-output-hk/cicero#67

Co-authored-by: John Ky <john.ky@iohk.io>

.github/workflows/markdown-links-ci-check.yml

@@ -0,0 +1,12 @@
+name: Check Markdown links
+
+on: push
+
+jobs:
+  markdown-link-check:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    - uses: gaurav-nelson/github-action-markdown-link-check@v1
+      with:
+        use-quiet-mode: yes