Add code review workflow (#14)

* Add code review workflow

* Fix typo in prompt message

* Update PROMPT message in cr.yml

---------

.github/workflows/cr.yml

@@ -0,0 +1,19 @@
+name: Code Review
+
+permissions:
+  contents: read
+  pull-requests: write
+
+on:
+  pull_request:
+    types: [opened, reopened, synchronize]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: anc95/ChatGPT-CodeReview@main
+        env:
+          GITHUB_TOKEN: ${{ secrets.GIT_TOKEN }}
+          OPENAI_API_KEY: ${{ secrets.OPENAI_API_KEY }}
+          PROMPT: "You are a software engineer who should review this pull request. You are currently typing in the comment section:"