Check for PR event (#37)

<!-- This is an auto-generated comment: release notes by openai -->
### Summary by OpenAI

**Release Notes**

This pull request adds a check for pull_request event before running the
`codeReview` function and displays a warning if it's not a pull_request
event. Additionally, try-catch blocks were added to handle errors while
posting and listing comments. This is a bug fix that ensures the
codeReview function runs only on pull_request events.
<!-- end of auto-generated comment: release notes by openai -->

Author: harjotgill