Prevent CI workflow on pure documentation changes, part 2 (KhronosGroup#2591)

Author: asuessenbach

.github/workflows/build-latest-spec.yml

@@ -7,6 +7,9 @@ on:
   workflow_dispatch:
   pull_request:
     branches: [ main ]
+    paths:
+      - '**'
+      - '!**.md'
 
 jobs:
   build: