update mirror.yaml workflow permissions (westpa#472)

Author: jeremyleung521

.github/workflows/mirror.yaml

@@ -4,15 +4,22 @@ on:
   schedule:
     # Once a month on the 28th day at 4 pm UTC, which is ~11 am EST.
     - cron: "00 16 28 * *"
+  workflow_dispatch:
 
 jobs:
   mirror-develop-to-westpa2:
     runs-on: ubuntu-latest
     name: Mirror develop branch to westpa2 branch
     steps:
+      - uses: actions/create-github-app-token@v1
+        id: app-token
+        with:
+          app-id: ${{ vars.BRANCH_MIRROR_APPID }}
+          private-key: ${{ secrets.BRANCH_MIRROR_SECRET }}
       - uses: actions/checkout@v4
         with:
           fetch-depth: 0
+          token: ${{ steps.app-token.outputs.token }}
       - name: mirroring step
         run: |
           git checkout westpa2