Adds ability to support array of alias values.

[DanHulton]

As of webpack 5, aliases can have an array of potential resolution paths, with the first entry in the array that resolves successfully being used. This allows users to define "fallback" paths to check.

However, this then breaks eslint, since it doesn't know what to do with a map, and simply picking one path or the other to default to could break under certain circumstances.

This patch allows aliases to have an array as their second parameter, which behave the same way that array paths in webpack do.

[coveralls]

Coverage remained the same at 100.0% when pulling 16175ec on DanHulton:alias_array into a69b482 on johvin:master.

[VdeVentura]

@johvin any chance we can take a look at this PR? I could make use of it :)

[VdeVentura]

@DanHulton, any chance of releasing this fork as a different NPM package? (if u didn't do it already)

[DanHulton]

@DanHulton, any chance of releasing this fork as a different NPM package? (if u didn't do it already)

I may have to. I've been using a link directly to my branch in git ("eslint-import-resolver-alias": "DanHulton/eslint-import-resolver-alias#alias_array") in the meantime, but the repo owner hasn't committed anything publicly since Feb, so they might be away for a while. If I do, I'll update this PR with a link.

[VdeVentura]

I started doing the same today 🙊

[DanHulton]

For now, I have published my fork of this package as eslint-import-resolver-alias-array to make it easier for people to use this code. I'll happily deprecate it once this PR is resolved.

[shaozj]

why not accept this pr，it's very useful!

[nickrobillard]

I would like to add that I am also using this PR in the form the eslint-import-resolver-alias-array NPM package and it is working exactly as expected. I will report issues here if I find them. Thank you @DanHulton.