Revamp and improve docs

[franciszekjob]

Feature Request

• update and improve quickstart section, especially part dedicated for contract declaration
• update usage of contract_class/compiled_contract_class amongst whole docs
• include code which shows reading the contracts from files

[Daveside9]

let me take this, i will update and enhance the quickstart guide, fix the contract declaration parts, standardize the usage of contract_class/compiled_contract_class, and add examples for reading contracts from files, ensuring the docs are clear and complete.
ETA: 1-2 working days

[DiegoFloresWenHao]

Let me handle this issue! I am an experience Python and Cairo Developer

[franciszekjob]

Hey, this task isn't for external contributors, please see issues with "good first issue" label, thanks.