Better typing for fixed length array arguments (ethers v5 target)

[zemse]

function payToTree(uint32[3] _rewardRatio) public;

Current:

_rewardRatio: ethers.BigNumberish[]

Desired:

_rewardRatio: [ethers.BigNumberish, ethers.BigNumberish, ethers.BigNumberish]

I think it would be nice to take into account about the array length (since ethers.js's ABI encoder also takes it into account ethers-io/ethers.js#1004).

I can work on this later this month or may be next month. Though, in case anyone is interested may do it :)

[zemse]

Actually, I just went ahead working on my project and realised that really wanted this small feature. So I just had to do it ‎😅