This is clearly NOT JSON format...

Despite many people's belief, presence of curly brackets, colons and quoted strings does NOT make a file JSON-formatted.
JSON format has strict syntax, see http://json.org for details.

What differs your format from JSON is:

• JSON must start with either curly bracket, or square bracket
  • i.e. your "export default" start of file makes it invalid JSON
• JSON strings must be enclosd in quotation marks
  • i.e. your "key" strings not being enclosed at all and "value" strings being enclosed in apostrophes make it invalid JSON

So you won't be able to process this file as-is using the standard JSON file type at all.
You may try your luck with the Supertext JSON file type, as it may be more benevolent to the syntax...

Otherwise you would need to process it using the plain text regex file type.
And you won't be able to handle the plurals... as this is apparently something that's handled by its mother application internally and there is no way to do any "sub-parsing" of the translatable strings in Studio.

Of course, you can write some pre- and post-processing script which will parse the source string and convert it to/from something else (e.g. XML) where you can have the plurals separated into separate segments.

The "export" keyword is not a 'standard' JavaScript, it's part of ECMAScript 6 and it's implemented in a few browsers only at this time.
Anyway...

As I mentioned, you can either parse it as-is as plain text, or create some pre-processing script to convert it to something else (e.g. XML), parse and translate that something else and then use a post-processing script to convert that translated something else back to the original format.

The "export" keyword is not a 'standard' JavaScript, it's part of ECMAScript 6 and it's implemented in a few browsers only at this time.
Anyway...

As I mentioned, you can either parse it as-is as plain text, or create some pre-processing script to convert it to something else (e.g. XML), parse and translate that something else and then use a post-processing script to convert that translated something else back to the original format.