Add auto-assign action. (#109)

.github/workflows/auto-assign.yml

@@ -0,0 +1,12 @@
+name: "Auto Assign"
+on:
+  pull_request:
+    types: [opened, ready_for_review]
+
+jobs:
+  add-reviews:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: kentaro-m/[email protected]
+        with:
+          configuration-path: ".github/some_name_for_configs.yml" # Only needed if you use something other than .github/auto_assign.yml