Add markdown link checker

.github/scripts/markdown-link-check-config.json

@@ -0,0 +1,8 @@
+{
+  "retryOn429": true,
+  "aliveStatusCodes": [
+    200,
+    403
+  ],
+  "ignorePatterns": []
+}

.github/scripts/markdown-link-check-with-retry.sh

@@ -0,0 +1,17 @@
+#!/bin/bash -e
+
+# this script helps to reduce sporadic link check failures by retrying at a file-by-file level
+
+retry_count=3
+
+for file in "$@"; do
+  for i in $(seq 1 $retry_count); do
+    if markdown-link-check --config "$(dirname "$0")/markdown-link-check-config.json" \
+                           "$file"; then
+      break
+    elif [[ $i -eq $retry_count ]]; then
+      exit 1
+    fi
+    sleep 5
+  done
+done

.github/workflows/build.yaml

@@ -29,6 +29,11 @@ jobs:
           GPG_PRIVATE_KEY: ${{ secrets.GPG_PRIVATE_KEY }}
           GPG_PASSWORD: ${{ secrets.GPG_PASSWORD }}
 
+  markdown-link-check:
+    # release branches are excluded to avoid unnecessary maintenance
+    if: ${{ !startsWith(github.ref_name, 'release/') }}
+    uses: ./.github/workflows/reusable-markdown-link-check.yml
+
   workflow-notification:
     needs:
       - build

.github/workflows/reusable-markdown-link-check.yml

@@ -0,0 +1,20 @@
+name: Reusable - Markdown link check
+
+on:
+  workflow_call:
+
+jobs:
+  markdown-link-check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Install markdown-link-check
+        run: npm install -g markdown-link-check
+
+      - name: Run markdown-link-check
+        run: |
+          find . -type f \
+                 -name '*.md' \
+                 -not -path './CHANGELOG.md' \
+               | xargs .github/scripts/markdown-link-check-with-retry.sh