Localization: internal change - include the language name (expressed in that same language) in the locale's JSON resource

https://github.com/daisy/ace/blob/4c6f5627ffdf14190342a3854d49b82df28aee49/packages/ace-core/src/l10n/localize.js#L12-L15

=> would become:

```javascript
fr: {
name: frJson.LOCALE_NAME,
translation: frJson
}
```

(`LOCALE_NAME` can be changed for any suitable well-defined key name, used consistently across all supported languages)

This internal change would mean that l10n contributions would include **all** translated labels inside the locale's JSON resource. For example, see this recent Pull Request:

https://github.com/daisy/ace/pull/246/files#diff-38adeefea9ae9024cab3ce220f321259