ci: support pr auto assign (#1004)

.github/auto_assign.yml

@@ -0,0 +1,8 @@
+# This is used for tracking in GitHub project.
+# See https://github.com/marketplace/actions/auto-assign-action
+
+# Set to true to add reviewers to pull requests
+addReviewers: false
+
+# Set to true to add assignees to pull requests
+addAssignees: author

.github/workflows/pr-auto-assign.yml

@@ -0,0 +1,12 @@
+name: Pull request auto assign
+
+# on: pull_request
+on:
+  pull_request:
+    types: [opened, ready_for_review]
+
+jobs:
+  add-reviews:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: kentaro-m/auto-assign-action@v1.2.4