Create bundler friendly builds

[tosuke]

Problem

Webpack4でバンドルすると，ビルドサイズが巨大になってしまう

Solution

• sideEffects: false を記述
• Webpack4はexport ~ fromのパターンを Tree Shaking できないので，esmをrollupで生成するようにした
• named export を追加
• core-js への依存を除去

Result

Tree Shakingできるようになった

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