docs: send user back with the correct type and fix typos

[namick]

What?

• Added async to the example authenticate function as it uses await.
• Updated example function to return the user with the collection property so type-checking works.

Why?

Better docs! 😄

TypeScript is expecting the authenticate function to return a User type from the payload package, and this requires the collection property from BaseUser.

[r1tsuu]

Replace spread that introduces copying overhead with mutation:

const user = usersQuery.docs[0] as unknown as User | undefined;
// handle null
user.collection = 'users'

The as cast is needed when using strict: true