Nuxt.js + Vuetifyのセットアップでcore-js関係の依存関係が見つからないと怒られた

##前置きtmpl
自分用メモです・・・至らないところはご容赦ください。
気付き / 学習ベースで適宜アップデートしますが、ご指摘を頂いた場合、直ちに適切な情報に差し替えます。

##怒られた
Nuxtをインストール。UI frameworkとしてVuetifyを選択。

```bash
npx create-nuxt-app <myproject>
```

その後、storybookなど、開発に必要なパッケージを追加していき、いざ

```bash
yarn dev
```

すると・・・

```bash
ERROR  Failed to compile with 32 errors                                                                                friendly-errors 08:19:15

These dependencies were not found:                                                                                      friendly-errors 08:19:15
                                                                                                                        friendly-errors 08:19:15
* core-js/modules/es6.array.find in ./.nuxt/client.js                                                                   friendly-errors 08:19:15
* core-js/modules/es6.array.iterator in ./.nuxt/client.js                                                               friendly-errors 08:19:15
* core-js/modules/es6.date.to-string in ./.nuxt/utils.js                                                                friendly-errors 08:19:15
* core-js/modules/es6.function.name in ./.nuxt/client.js                                                                friendly-errors 08:19:15
* core-js/modules/es6.object.assign in ./.nuxt/client.js                                                                friendly-errors 08:19:15
* core-js/modules/es6.object.keys in ./.nuxt/utils.js                                                                   friendly-errors 08:19:15
* core-js/modules/es6.object.to-string in ./.nuxt/axios.js, ./.nuxt/components/nuxt-link.client.js                      friendly-errors 08:19:15
* core-js/modules/es6.promise in ./.nuxt/client.js                                                                      friendly-errors 08:19:15
* core-js/modules/es6.regexp.constructor in ./.nuxt/utils.js                                                            friendly-errors 08:19:15
* core-js/modules/es6.regexp.match in ./.nuxt/client.js                                                                 friendly-errors 08:19:15
* core-js/modules/es6.regexp.replace in ./.nuxt/utils.js, ./.nuxt/components/nuxt.js                                    friendly-errors 08:19:15
* core-js/modules/es6.regexp.search in ./.nuxt/utils.js                                                                 friendly-errors 08:19:15
* core-js/modules/es6.regexp.split in ./.nuxt/utils.js, ./node_modules/babel-loader/lib??ref--2-0!./node_modules/vue-loader/lib??vue-loader-options!./.nuxt/components/nuxt-build-indicator.vue?vue&type=script&lang=js&
* core-js/modules/es6.regexp.to-string in ./.nuxt/utils.js                                                              friendly-errors 08:19:15
* core-js/modules/es6.string.includes in ./.nuxt/client.js, ./.nuxt/components/nuxt-link.client.js                      friendly-errors 08:19:15
* core-js/modules/es6.string.iterator in ./.nuxt/App.js                                                                 friendly-errors 08:19:15
* core-js/modules/es6.string.repeat in ./.nuxt/utils.js                                                                 friendly-errors 08:19:15
* core-js/modules/es6.string.starts-with in ./.nuxt/utils.js                                                            friendly-errors 08:19:15
* core-js/modules/es6.symbol in ./.nuxt/utils.js, ./.nuxt/components/nuxt-link.client.js                                friendly-errors 08:19:15
* core-js/modules/es7.array.includes in ./.nuxt/client.js, ./.nuxt/components/nuxt-link.client.js                       friendly-errors 08:19:15
* core-js/modules/es7.object.get-own-property-descriptors in ./.nuxt/utils.js                                           friendly-errors 08:19:15
* core-js/modules/es7.promise.finally in ./.nuxt/client.js                                                              friendly-errors 08:19:15
* core-js/modules/es7.symbol.async-iterator in ./.nuxt/client.js, ./.nuxt/components/nuxt-link.client.js                friendly-errors 08:19:15
* core-js/modules/web.dom.iterable in ./.nuxt/App.js, ./.nuxt/components/nuxt-link.client.js
```

いっぱい怒られた！
その後、怒られの通りcore-jsが入ってないのかな？と以下を試みる。

```bash
yarn add core-js
```

解決せず・・・同様のエラーが再表示。

##原因と解決

どうやらcore-jsを3系→2系にダウングレードする必要があるらしい。
参考：https://github.com/nuxt/nuxt.js/issues/5315

再インストール。

```bash
yarn add core-js@2.6.9
```

再インストール後のpackage.json

```json:package.json
{
  "name": "myproject",
  "version": "1.0.0",
  "description": "My Nuxt.js project",
  "author": "Shun Kimura",
  "private": true,
  "scripts": {
    "dev": "nuxt",
    "build": "nuxt build",
    "start": "nuxt start",
    "generate": "nuxt generate",
    "storybook": "start-storybook -p 9001 -c .storybook"
  },
  "dependencies": {
    "@nuxtjs/axios": "^5.3.6",
    "@nuxtjs/pwa": "^3.0.0-0",
    "babel-preset-vue": "^2.0.2",
    "core-js": "2.6.9",
    "nuxt": "^2.0.0"
  },
  "devDependencies": {
    "@nuxtjs/vuetify": "^1.0.0",
    "@storybook/vue": "^5.2.1",
    "babel-loader": "^8.0.6",
    "vue-loader": "^15.7.1",
    "vue-template-compiler": "^2.6.10"
  }
}
```

dev server起動。

```bash
yarn dev
```

動いた！