Export supertokens config type

[rishabhpoddar]

This can help users create the config in its own function. Something like:

import supertokens from "supertokens-auth-react";
import {SuperTokensConfig} from "supertokens-auth-react/types";
getConfig(): SuperTokensConfig => {
   return { ... }
}

supertokens.init(getConfig())