Generate documentation for smart contracts

[pdyraga]

We want the documentation to be generated as a part of the CI flow and automatically uploaded to https://docs.threshold.network/contracts. All the contracts and functions are quite heavily documented. We need to use some tooling (e.g. OpenZeppelin has one) to generate HTMLs similar to https://docs.openzeppelin.com/contracts/4.x/api/token/erc20#IERC20.

This task has several smaller items, I recommend we start with choosing a tool and then integrating it with a CI. The infrastructure work with the upload should be the last step.