Language Translation.
Translations are resources that can be loaded and unloaded on demand. They map a string to another string.
$DOCS_URL/03_usage/12_i18n/01_internationalizing_games.md
$DOCS_URL/03_usage/12_i18n/03_locales.md
Virtual method to override [method get_message].
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.