[Feature] add replaceTranslations method

[javleds]

Hi!

In order to allow the users to replace all the translations for a single key in one go, we add the replaceTranslations function which forgets all the translations for the key provided and registers the new values.

public function replaceTranslations(string $key, array $translations)

Here's an example:

$translations = ['en' => 'hello', 'es' => 'hola'];

$newsItem->setTranslations('hello', $translations);
$newsItem->getTranslations(); // ['en' => 'hello', 'es' => 'hola']

$newTranslations = ['en' => 'hello'];

$newsItem->replaceTranslations('hello', $newTranslations);
$newsItem->getTranslations(); // ['en' => 'hello']

If something is missing or do you consider that we should change something, please let me know.

[freekmurze]

Thanks!