[FEAT] Banner to show it's a demo project

[brunobritodev]

Is your feature request related to a problem? Please describe.
No

Describe the solution you'd like
A banner to show visitors the site is just a demo and not a real store. The banner must have a link to this repository.

[Kirito-Excalibur]

....link to the website?

[brunopbarrote]

....link to the website?

At the bottom of README, at "We are Online" there is a link. Or here

[brunobritodev]

I mean something like this snapshot:

[Kirito-Excalibur]

Sure. I will get it done.