Avoid unnecessary republishes

Can always use workflow_dispatch if needed

Author: Toby222

.github/workflows/mdbook.yml

@@ -9,6 +9,10 @@ on:
   push:
     branches:
     - main
+    paths:
+    - 'src/**.md'
+    - 'book.toml'
+    - 'theme/**'
 
   # Allows you to run this workflow manually from the Actions tab
   workflow_dispatch: