Add an example for using named imports with trackExtraHooks

[xepozz]

No description provided.

[CJamesKeller]

As a user, I agree that this would be a helpful addition.

[vzaidman]

@xepozz isn't useSelector a named import? What is this example adding to the readme?

[xepozz]

There is some misleading because a lot of people may not know about redux and don't use it in their project.
In general it may be confusing to see [someObject, 'familiar-method'] structure for new users, so I think my example is more informative then existed.
And one more point that it's a bit compact form that the existing one. 2 line vs 1.

In my project I use my variant and it seems good to me :)