Ability to use custom templates

[jonwalstedt]

I would like to be able to create custom templates to use with create-app.

Describe the solution you'd like
I would like to be able to run something like yarn create @vitejs/app my-new-app --template ./my-local-template or yarn create @vitejs/app my-new-app --template @my-co/my-custom-vitejs-kickstarter-template to generate the base for my application.

Currently there is a hardcoded check in https://github.com/vitejs/vite/blob/main/packages/create-app/index.js isValidTemplate = availableTemplates.includes(template) that only allows for templates in the availableTemplates array.

[patak-dev]

I think you could use https://github.com/Rich-Harris/degit to quickly start your project copying a repository.

[yyx990803]

Just use degit. @vitejs/app is only for official templates.