Parse signed integers

[metalboyrick]

Issue Overview

Starknet.js currently does not have any parsing ability for signed integers, we might need to implement our own parsers to process them.

Proposed Solutions or Ideas

refer these resources for information on how to do:

• https://docs.starknet.io/architecture-and-concepts/smart-contracts/serialization-of-cairo-types/#data_types_of_252_bits_or_less
• https://github.com/starknet-io/starknet.js/issues/1014
• https://github.com/starknet-io/starknet.js/pull/1177

[metalboyrick]

will wait for starknet.js implementation