Add official Github action for openapi-diff

Openapi-diff is well suited to be integrate into Github actions in order to:

• Highlight breaking in a pull request
• Document changes in OpenAPI
• etc.

For example, today we have an internal github repo which on every commit triggers generating Redoc OpenAPI documentation and publishes it to Github pages for the repository. In this documentation we'd like to include a openapi-diff markdown report of the changes.

Or, when ever we do a pull request we want to review the changes made. Openapi-diff will allow us to identify automatically breaking changes.

There are a couple of unofficial limited Github actions based on other openapi diff tool

• https://github.com/marketplace/actions/openapi-review
• https://github.com/marketplace/actions/openapi-diff

首先检查仓库现有的入口点以及发布或自动化配置；该 issue 未指定任何文件或测试。将请求的行为与链接的非官方 actions 进行比较，并确定官方 action 应如何提供 OpenAPI diff 结果和 breaking-change 检查。完成的标准是：为 pull-request 和报告生成工作流记录并验证一个可用的 GitHub Action。