Improve docs on precompiled-contracts in kiichain-docs and on repo

[jhelison]

Is your feature request related to a problem? Please describe.
Precomplies are missing description and readmes explaining their implementation and usability

Describe the solution you'd like
New readmes for the precompiles and description on kiichain-docs

Describe alternatives you've considered
Reading the code

Additional context
Precompiles can be found here: https://github.com/KiiChain/kiichain/tree/main/precompiles