Improve documentation

[jpcenteno]

I reassigned this ticket to @fkrause98 since it is related to the zksync-web3-rs repo.

Fran, please link here or there the URLs for your PRs

[fkrause98]

Current docs PRs:

• https://github.com/lambdaclass/zksync-web3-rs/pull/114
• https://github.com/lambdaclass/zksync-web3-rs/pull/112