Language Translation.
Translations are resources that can be loaded/unloaded on demand. They map a string to another string.
https://docs.godotengine.org/en/3.1/tutorials/i18n/internationalizing_games.html
https://docs.godotengine.org/en/3.1/tutorials/i18n/locales.html
Adds a message if nonexistent, followed by its translation.
Erases a message.
Returns a message's translation.
Returns the number of existing messages.
Returns all the messages (keys).
The locale of the translation.