Cannot handle i18n function that receives multiple arguments

Example: For this code snippet

```
${i18n.tr('Lorem {0}. Dolor sit amet.', 'Ipsum')}
```

it outputs the string `Lorem {0}. Dolor sit amet.', 'Ipsum`, ignoring the actual quotes.

(I used the command `node xgettext-regex.js src -f "(?:i18n.tr|I18n.marktr|i18n.trn)" -o po/keys.pot`)

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While this example is not really practical, the regex fails to match anything if additional arguments besides string literals are provided. And for pluralize calls like `${i18n.trn('Blubber', 'Blubbers', 7)}`, both string literals should be matched.