documentation: order of middleware

[driesdesmet]

I ran into the issue where I had put the ''asymmetric_jwt_auth.middleware.JWTAuthMiddleware' before 'django.contrib.auth.middleware.AuthenticationMiddleware', and because django's authentication middleware overwrites request.user every time, I didn't get the desired authentication. Maybe this is obvious to a seasoned django developer, but I think putting this somewhere in the docs, could help other users.

Thanks.