Support create-nextra-app

[devjiwonchoi]

@shuding @B2o5T
Since nextra has handy templates: docs and blog, we would be able to add an option extending fork the templates.
By doing so, the user will be able to choose the following options:

1. The initial project name
2. TypeScript
3. Tailwind
4. Template<docs | blog | custom>

I you approve this feature, then I'm willing to work on it.