Most used cases for overlay are Alert and Toast which requires to see behind the overlay

* Update installing doc

* Rename style articles

* add docs prefix to getting started articles

* Rename all the things. Consistent id format

* Split docs and api

* Fix links

Co-authored-by: Guy Carmeli <guyc@wix.com>

* Completely rewritten the docs from scratch
* More coherent separation between guides and API documentation
* Switched to Docusaurus 2 since Docsify is deprecated
* More code samples
* Images and animated gifs were added where appropriate improve clarity (more will be added in the future)