⚡️ Optimise mul_div Method

[pcaversaccio]

We simplify the twos calculation in mul_div in a similar way as proposed here. This will save one operation.

Explanation: -x in two's complement (where x is uint256) is defined as ~x + 1 which is max_value(uint256) - x + 1. Thus, -x -> 0 + max_value(uint256) - x + 1 -> unsafe_sub(0, x) as long as x>=1 holds.

Furthermore, we bump eslint-config-prettier, ethers, and prettier to the corresponding latest versions. Eventually, the submodule openzeppelin-contracts is bumped to the latest available commit.

🐶 Cute Animal Picture