OSS Stock Trading Team Project Start

## 목적
Create 2023OSS Team Project "StockTrading"
## 작업 상세 내용
Issue template 추가

## Reference
README.md 파일을 수정해봐요 :)

The issue asks to add an issue template and modify the README.md file. Start by looking at the repository's .github folder for existing templates and the README.md content. Determine what information should be added to the README for the stock trading project. Check if there are any contributing guidelines or project structure details to reference.

索引モデルが issue の本文から書いたものです。