Add ENSIP-15: Name Normalization Standard Support

I would like to add ENSIP-15 support. (I can’t include links?)

The modification is very simple (ethers, isValidDomainName(), and corresponding unit tests) but I’m unsure how to patch the active version of ethers under the current build system.

I need to replace the single include of {nameprep} from @ethersproject/strings/lib/idna.js with {ens_normalize as nameprep} from @adraffy/ens-normalize.

Is there an acceptable way for me to patch this?

This change is included by default in ethers v6, but that would involve a large code change. I will reach out to Ricmoo to see if there’s a way to get this change into an ethers v5 update.