[CI] Feature: Auto assign pr author to pr (#5661)

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## PR-Codex overview
This PR introduces a new GitHub Actions workflow for automatically assigning authors to pull requests when they are opened or reopened.

### Detailed summary
- Added a new workflow file: `.github/workflows/auto-assign.yml`
- Defined the workflow name as `Auto Author Assign`
- Set the trigger for the workflow on `pull_request` events for types `opened` and `reopened`
- Specified permissions for pull requests as `write`
- Created a job named `assign-author` that runs on `ubuntu-latest`
- Included a step to use the action `toshimaru/auto-author-assign@v2.1.1`

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Author: gregfromstl

.github/workflows/auto-assign.yml

@@ -0,0 +1,14 @@
+name: Auto Author Assign
+
+on:
+  pull_request:
+    types: [ opened, reopened ]
+
+permissions:
+  pull-requests: write
+
+jobs:
+  assign-author:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: toshimaru/auto-author-assign@v2.1.1