Add 'why use rx-queue' section to readme

[crunchie84]

Your package seems well formed and contains a lot of documentation :+1:

But; could you add a section to the README.md of your package explaining what the benefits are of using rx-queue implementations over their naive/native implementations?

[huan]

Thanks for the request to make this project better.

However, I got really busy and have no time to maintain that recently.

So please help yourself to add that documentation if you like: PR is welcome.