Updating the session cookie

[patrick-hofmann]

The session cookie is not updated automatically if the data within the session is not updated.

Repro:
in playground nuxt.config.js set runtimeConfig session to:

runtimeConfig: {
session: {
maxAge: 60,
cookie: {
maxAge: 10,
},
},
},

then login using password. Refresh the page serveral times within 10 seconds, after 10 seconds -> the session is gone (because the cookie is not set in the server response).

PR #255 solves this issue