feat: Add 'most-similar-by-key' mode for TargetPickingStrategy

[johanninos]

A Vue project might have the following file structure:
locales

  ├── en
  |   ├── common.json
  |   ├── buttons.json
  |   ├── ...
  |   └── index.ts
  ├── de-DE
  |   ├── common.json
  |   ├── buttons.json
  |   ├── ...
  |   └── index.ts
  └── <country-code>
      ├── common.json
      ├── buttons.json
      ├── ...
  |   └── index.ts

  // locales/en/index.ts
  import buttons from 'bottons.json';
  ......

  export default {
      common,
      buttons,
  }

   // in components
   {{ t('buttons.someType.someName') }}
   {{ t('common.someType.someName') }}

In the code, we can use t('buttons.someType.someName') or t('common.someType.someName') in the components to retrieve translated text. However, it is inconvenient to have to choose the file to save every time.

I mentioned the most-similar mode, but noted that it is not suitable because common.xxx can be in any folder path.

I considered extracting the namespace to determine the target file, but found that namespaces can be complicated. For example, the namespaces configuration is ['{locale}/{namespaces}.*', 'zh-cn/hello/world/messages.json', 'hello/world/messages', 'zh-cn'].
So, you found an easier and more flexible way to resolve it by matching the most similar key. The logic is the same as most-similar, except that the findBestMatchFile argument is changed from fromPath to keypath.

When using common.*, it will match the common.json file.
When using buttons.*, it will match the buttons.json file.

I hope this PR can be merged soon, as it can solve my problem and save development time.
Thank you.