Add documentation for Redis Store with example

[xstevenyung]

Thanks to @Octo8080X work, we now have access to a Redis store for session.

We need to add some documentation (inspiration can be taken from the PR #3) to help people understand how to work with it.

[Octo8080X]

Thanks to @xstevenyung.
I'll add the one I incorporated as an example, but what do you think?

[xstevenyung]

The one in your PR would be a great start to the documentation!