Configurable Session ID

[wyattjoh]

Next.js is currently exploring instrumenting API's like Math.random() and others that add "entropy" to a given prerendered page, and accesses of these API's currently print a warning to the console. I'm hoping that y'all are open to making the sessionId for createStore be something that can be explicitly provided to ensure that we can bypass this particular issue.

[davidkpiano]

Yes, I am. That's a great idea. I can implement this later, unless you want to try doing this? Would love a PR.