write Smart contract documentation

[peterjah]

Copy pasta from user feedback:

I've started the process of learning about MASSA and evaluating strategies for the POC. Some feedback on the MASSA Smart Contract docs:

• I suggest adding a section titled something like "Migrating from Solidity".. or "Comparison with Solidity" that goes through a non-trivial Solidity example and how to do something similar with MASSA.

The majority of devs with smart contract experience are most likely coming from a Solidity background and may not have used WASM before.

• A section that outlines how to structure a smart contract and basic features like:

  • What determines visibility of a function? (i.e. public, internal, private in Solidity)
  • How to pass constructor arguments
  • Functions with multiple args and types
  • Sending value (i.e. payable in Solidity)
  • Error handling, throwing errors
  • Inheritance, interfaces
  • Imports
  • etc.

Perhaps this is all in the WASM docs and it's the same, but it would be worthwhile to repeat the basics and describe where things are different.

I was pretty confused after looking at the docs. The Trading Bot video was helpful but it's over an hour of content and and not structured like a tutorial. It's also a year old and I'm sure much has changed since.