Only exclude markdown on the top level and everything inside 'Proposals/' path

Author: itingliu

.github/workflows/pull_request.yml

@@ -4,7 +4,8 @@ on:
   pull_request:
     types: [opened, reopened, synchronize]
     paths-ignore:
-      - '**.md'
+      - '*.md'
+      - 'Proposals/**'
 
 jobs:
   tests: