chore: 로켓 이모지 추가

Author: dlsrks1021

.github/workflows/slack-notify-pr-open.yml

@@ -16,7 +16,7 @@ jobs:
           SLACK_ICON: https://github.com/github.png
           MSG_MINIMAL: ref,event
           SLACK_COLOR: '#36a64f'
-          SLACK_TITLE: 'New Pull Request'
+          SLACK_TITLE: 'New Pull Request 🚀'
           SLACK_MESSAGE: |
             #${{ github.event.pull_request.number }} ${{ github.event.pull_request.title }}
             🔗 ${{ github.event.pull_request.html_url }}