Separete module

[azu]

https://github.com/textlint-ja/textlint-rule-ja-unnatural-alphabet/blob/master/src/textlint-rule-ja-unnatural-alphabet.js#L43-L59

[azu]

• モジュールとして分ける
• match-indexに ( ) ナシを可能にする

[azu]

insteadof

• sindresorhus/execall: Find multiple RegExp matches in a string
• tc39/String.prototype.matchAll: ES Proposal, specs, tests, reference implementation, and polyfill/shim for String.prototype.matchAll