Add "Docs-Polish" as the first task

[hsluoyz]

The Task struct is created at:

https://github.com/casbin/casibase/blob/ef1cf307b823b9e1111051182bd89369d9d78b3c/object/task.go#L24-L33

Other parts should also be completed like: ac76b1f

Port: casbin/casdoc#1 to this repo

• Application is Docs-Polish (use Antd's Select)
• Provider is the model provider's name like: provider_openai_key (from https://ai.casbin.com/providers/provider_openai_key)
• Path is the Docusaurus docs repo path, like: C:/casdoor-website

[casbin-bot]

@tangyang9464 @JalinWang @imp2002