typescript support for customization config

[dulltackle]

Maybe we can add the type of our customization config to the build-in config type of [tailwindcss][https://github.com/tailwindlabs/tailwindcss/blob/4a745439f010aca2ea24bb7fd9ab0ac3e15a40c1/types/config.d.ts]. So user can get config suggestion from IDE directly.