Auto Rebase Github Action (#3774)

* Auto Rebase Github Action

* Update .github/workflows/rebase.yml

Place env at the beginning of job.

Co-authored-by: Tim Buckley <timothypbuckley@gmail.com>

Co-authored-by: Tim Buckley <timothypbuckley@gmail.com>

.github/workflows/rebase.yml

@@ -0,0 +1,22 @@
+# https://github.com/marketplace/actions/automatic-rebase  (https://github.com/cirrus-actions/rebase)
+name: Automatic Rebase
+
+on:
+  issue_comment:
+    types: 
+      - created
+
+env:
+  GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+jobs:
+  rebase:
+    name: Rebase
+    if: github.event.issue.pull_request != '' && startsWith(github.event.comment.body, '/rebase')
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@master
+      with:
+        fetch-depth: 0
+    - name: Automatic Rebase
+      uses: cirrus-actions/rebase@1.3.1