fix branch name

Author: maxbachmann

.github/workflows/documentation.yml

@@ -3,7 +3,7 @@ name: documentation
 on:
   push:
     branches:
-      - master
+      - main
 
 jobs:
   build_docs:
@@ -15,4 +15,4 @@ jobs:
     - uses: peaceiris/actions-gh-pages@v3
       with:
         github_token: ${{ secrets.GITHUB_TOKEN }}
-        publish_dir: ./doxygen/html
+        publish_dir: ./doxygen/html