fix rebase.yml

.github/workflows/rebase.yml

@@ -1,14 +1,17 @@
-on:
+name: Automatic Rebase
+# https://github.com/marketplace/actions/automatic-rebase
+
+on: 
   issue_comment:
     types: [created]
-name: Automatic Rebase
+
 jobs:
   rebase:
     name: Rebase
     if: github.event.issue.pull_request != '' && contains(github.event.comment.body, '/rebase')
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@master
+    - uses: actions/checkout@v2
       with:
         fetch-depth: 0
     - name: Automatic Rebase