i18n locale file builder - Issue 120

[YassSMR]

We had a hard time finding a bookstore that met the import requirements you mentioned.
But we finally found a library that allowed us to do so.

To do the translations, you have to download the xlsx file in the extension directory and then run the npm i18 script.

Fixes #120

Co-authored: @toto101230

[ear1grey]

This looks good, though the use of Excel is a surprise.
For maintainability going forward we'll need two key changes.

1. The code should read values directly from this spreadsheet using the Google sheets API. (We can set the sheet to be readable by anyone, so only named editors can amend it.)
2. If any of the locales marked as ready does not contain a complete list of translations the program should process.exit(100) so we can include this in the release process and the build ill not succeed if the languages marked as released are not fully translated. This potentially makes the release process longer as more languages are added, but it means the interface won't break for anyone once a locale is released.