docs: ABI for all possible data types

[ermvrs]

Add a document md file for all possible abis from starknet and ethereum. In starknet, it has to have both return and parameters.

The most important data types are complex types. We already have basic type conversions. We need documentation for types like an array of basic types, an array of arrays, an array of custom structs, custom structs, bytes31, and bytes array.

This documentation lets us show the most idiomatic way to approach converting custom data types to basic types, then we can convert to Ethereum type.

Add an MD file to the docs folder.

[ermvrs]

Example types

 Supported Cairo Types

Abiwan supports all of Cairo types, here's the mapping between Cairo types and Typescript types

Primitive Types

Cairo	TypeScript
felt252	string \| number \| bigint
u8 - u32	number \| bigint
u64 - u256	number \| bigint \| U256
ContractAddress	string
EthAddress	string
ClassHash	string
bytes31	string
ByteArray	string
bool	boolean
()	void

 Complex Types

Cairo	TypeScript
Option<T>	T \| undefined
Array<T>	T[]
Span<T>	T[]
tuple (T1, T2, ..., Tn)	[T1, T2, ..., Tn]
struct	an object where keys are struct member names
enum	a union of objects, each enum variant is an object

[ermvrs]

Please also tracking page for which types we support completely