Update jekyll-gh-pages.yml

Better filtering for when the workflow should be run

.github/workflows/jekyll-gh-pages.yml

@@ -5,6 +5,8 @@ on:
   # Runs on pushes targeting the default branch
   push:
     branches: ["main"]
+    paths:
+      - '**.md'
 
   # Allows you to run this workflow manually from the Actions tab
   workflow_dispatch: