docs: Style Guide - Snake case for contracts

[PatrickAlphaC]

As of right now, the docs have no mention of style guide for contract names.

It'll be good to add snake_case to the style guide for contract names.

[AlbertoCentonze]

Not sure the docs should be opinionated about this.

I like to name my contracts in PascalCase and then import them with a snek_case alias, for instance:

import MyContract as my_contract