Create a CI/CD Pipeline

This issue proposes setting up a CI/CD pipeline that automates
- testing the application
- building the application as a Docker image.
- deploying the application to digital ocean
Once built, the image should be pushed to GitHub's image registry for easy access and deployment. This will help streamline the development process, ensuring that tests are run on each commit and that an up-to-date image is always available in the registry.

## Objectives:
- Set up a CI/CD pipeline using GitHub Actions.
- Run tests.
- Build a Docker image of the app upon successful testing.
- Push the built Docker image to GitHub's container registry with appropriate tags for easy versioning.
- Include a README update to guide users on accessing and using the pre-built images.

You can reference the [badgingAPI repo](https://github.com/badging/badgingAPI)

首先检查仓库现有的测试和应用设置，然后查看所请求的 GitHub Actions workflow 和 Docker 镜像流程。README 应记录访问预构建镜像的方法。当测试在每次提交时运行、成功的构建被标记并推送到 GitHub 的容器注册表，并且处理 DigitalOcean 部署时，即视为完成。

由索引模型根据 Issue 内容生成。