chore: Add PR notification

[jamesnrokt]

Instructions

1. PR target branch should be against development
2. PR title name should follow this format: https://github.com/mParticle/mparticle-workflows/blob/main/.github/workflows/pr-title-check.yml
3. PR branch prefix should follow this format: https://github.com/mParticle/mparticle-workflows/blob/main/.github/workflows/pr-branch-check-name.yml

Summary

• Add notification after PR completes

Testing Plan

• N/A

Reference Issue (For mParticle employees only. Ignore if you are an outside contributor)

• N/A

[Copilot]

Pull Request Overview

This PR adds a Google Chat notification system that triggers when pull requests are opened, along with workflow concurrency controls and necessary permissions for the GitHub Actions workflow.

• Adds concurrency control to prevent multiple workflow runs for the same PR
• Configures required permissions for the workflow to access GitHub resources
• Implements a notification job that sends PR updates to Google Chat

Comments suppressed due to low confidence (1)

.github/workflows/pull-request.yml:53

• [nitpick] The secret name 'GCHAT_PRS_WEBHOOK' uses inconsistent naming with a mix of abbreviations. Consider using a more descriptive name like 'GOOGLE_CHAT_PR_WEBHOOK' for better clarity.

      gchat_webhook: ${{ secrets.GCHAT_PRS_WEBHOOK }}

[BrandonStalnaker]

LGTM