feature request: single assets in i18n builds

### Command

build

### Description

Hi.
Currently angular just copy assets folder to every localized build. This leads to enormous dist size (in my case every locale with assets weigths 180MB, which can be multiplied by 15 locales).

### Describe the solution you'd like

My proposal is to put assets folder in root directory, instead of copying it inside every built locale, and symlink it inside every locale. This will give us better build times, and also will fix issues where developers use absolute urls to assets, eg:

```

```

My solution will give developers a way to use localized builds in mobile apps development (with capacitor for example; for now it’s strange to publish mobile app which weights over 2gb), better build times (no need to copy assets to every locale), better deploy times (transfer 180mb instead of 2.7GB)

### Describe alternatives you've considered

Currently, the only issue i encounter, is absolute path usage (described it in my example with img src). I make symlink to get this working:

/en/assets -> /assets

ビルドコマンドから始め、各ローカライズ済みビルドにどのように assets がコピーされるかを追跡します。現在の locale ごとの出力を、提案されている root レベルの assets および locale symlink と比較します。assets が重複せず、絶対 /assets URL が引き続き機能すれば完了です。

索引モデルが issue の本文から書いたものです。