New chapters

I added three new chapters to the documentation: Locale-aware formatting, Floating components, Media and Embeds.

Also, I split and extended with new info the previous Apply theme page into the Theme and style chapter.

• Locale-aware formatting is about various components that allow displaying dates, numbers, units, country and currency names localized and properly formatted.
• Floating components are rendered on top of the main content flow, thus gaining more user attention. This behaviour is useful for varios notifications, modal and navigation elements.
• Media and Embeds contains components designed to embed external content such as images, videos, audios, maps, and other web pages within your application.