Update main.yml

Author: ZhaoQi99

.github/workflows/main.yml

@@ -4,6 +4,7 @@
 name: Python package
 
 on:
+  workflow_dispatch:
   push:
     branches:
       - main
@@ -26,6 +27,7 @@ jobs:
       uses: actions/setup-python@v3
       with:
         python-version: ${{ matrix.python-version }}
+        os: ubuntu-latest
     - name: Install dependencies
       run: |
         pip install --upgrade pip