another hint for saveMissing

README.md

@@ -30,6 +30,8 @@ Did you wait 5-10 seconds before refreshing the locize UI? It may take a couple
 
 Per default only `localhost` is allowed to send missing keys ([or update missing keys](https://www.i18next.com/overview/configuration-options#missing-keys)) (to avoid using this feature accidentally [in production](https://docs.locize.com/guides-tips-and-tricks/going-production)). If you're not using `localhost` during development you will have to set the `allowedAddOrUpdateHosts: ['your.domain.tld']` for the [backend options](https://github.com/locize/i18next-locize-backend#backend-options).
 
+It's also recommended to set the `fallbackLng` equal to the source language defined in locize. i.e. if your source language in locize is `de`, set the fallbackLng also to `de`.
+
 
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