chore: migrate code to ESM (#73)

node_modules/undici/lib/mock/pluralizer.js

@@ -1,29 +0,0 @@
-'use strict'
-
-const singulars = {
-  pronoun: 'it',
-  is: 'is',
-  was: 'was',
-  this: 'this'
-}
-
-const plurals = {
-  pronoun: 'they',
-  is: 'are',
-  was: 'were',
-  this: 'these'
-}
-
-module.exports = class Pluralizer {
-  constructor (singular, plural) {
-    this.singular = singular
-    this.plural = plural
-  }
-
-  pluralize (count) {
-    const one = count === 1
-    const keys = one ? singulars : plurals
-    const noun = one ? this.singular : this.plural
-    return { ...keys, count, noun }
-  }
-}