Only run markdown-link-check when markdown files are updated

Author: jeffhandley

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

@@ -1,10 +1,12 @@
 name: Check Markdown links
 
 on:
-    push:
-      branches: [ "main" ]
-    pull_request:
-      branches: [ "main" ]
+  push:
+    branches: [ "main" ]
+    paths: "**.md"
+  pull_request:
+    branches: [ "main" ]
+    paths: "**.md"
 
 jobs:
   markdown-link-check: