Collect all tools under one namespace in umd.

[dimensi]

In webpack configs you not have standard naming convension for library name.
https://github.com/editor-js/image/blob/master/webpack.config.js#L45 here you set ImageTool,
https://github.com/editor-js/list/blob/master/webpack.config.js#L39 but here you set Link.
Webpack allow create namespaces for library. I think you must collect all tools under EditorJS namespace.

// webpack.config.js
{
  output: {
    path: __dirname + '/dist',
    publicPath: '/',
    filename: 'bundle.js',
    library: ['EditorJS', 'List'],
    libraryTarget: 'umd'
  }
}

Because EditorJS it's class you not get conflict of namespace, all tools will be collect as static methods.