Add documentation 'CashScript for Solidity developers'

[mr-zwets]

Given that solidity is the industry standard, it would be good if in the 'about' section we can have a page 'CashScript for Solidity developers' which explains the differences of contract development in development and deployment.

This would be a way for experienced smart contract developers to get up to speed faster by highlighting the key differences, maybe with the help of a comparison table.