create subdirectory doc/manual

Author: cadenmyers13

.github/workflows/docs.yml

@@ -6,6 +6,10 @@ on:
       - main
   release:
 
+  pull_request:
+    branches:
+      - main
+
 jobs:
   test:
     runs-on: ubuntu-latest
@@ -37,6 +41,7 @@ jobs:
         run: make -C doc/manual html
 
       - name: Deploy
+        if: github.event_name == 'push' && github.ref == 'refs/heads/main'
         uses: peaceiris/actions-gh-pages@v3
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}