add auto assign PR assignee

.github/workflows/pr_assignee.yml

@@ -0,0 +1,19 @@
+name: Assign PR to creator
+
+# Due to GitHub token limitation, only able to assign org members not authos from forks.
+# https://github.com/thomaseizinger/assign-pr-creator-action/issues/3
+
+on:
+  pull_request:
+    types: [opened]
+    branches-ignore:
+      - l10n_dev
+
+jobs:
+  automation:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Assign PR to creator
+      uses: thomaseizinger/assign-pr-creator-action@v1.0.0
+      with:
+        repo-token: ${{ secrets.GITHUB_TOKEN }}