Add checkout options to the example

These two lines are critical to the function of the Action, please add to the readme so the fix in ad-m#44 doesn't get lost.

README.md

@@ -20,6 +20,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@master
+      persist-credentials: false # otherwise, the token used is the GITHUB_TOKEN, instead of your personal token 
+      fetch-depth: 0 # otherwise, you will failed to push refs to dest repo
     - name: Create local changes
       run: |
         ...