Define strategy to extend core components styles

[romelperez]

Core components do not support internal elements styles extension. To properly customize components, a simple way to extend elements styles is required.

A possible approach could be to provide a component prop styles?: Record<string, CSSObject> to merge with the internal built-in styles. The following features would also be useful:

• Theme and component props access.
• Media Queries deep merge/extension.
• Simple React prop internal manipulation and no HOCs.

[romelperez]

Closed due to #46 (comment)