ci: add link check workflow

.github/workflows/link-check.yml

@@ -0,0 +1,20 @@
+name: Check Markdown for Broken Links
+
+on:
+    schedule:
+        # 01:30 every day
+        - cron: "30 1 * * *"
+    # Allows this workflow to be run manually from the Actions tab
+    workflow_dispatch:
+
+jobs:
+    link-check:
+        name: Link Check
+        runs-on: ubuntu-latest
+        steps:
+            - uses: actions/checkout@v2
+            - uses: actions/setup-node@v2
+              with:
+                  node-version: 14.x
+            - name: Run Linkinator
+              run: npx linkinator *.md --skip 'https://github.com/Fdawgs/.*/issues/, https://github.com/Fdawgs/.*/commit/, http://0.0.0.0'