The default project locale used when no other locale is selected.
This locale is the fallback that LocalizationSettings.InitializeAsync selects when none of the LocalizationSettings.StartupSelectors returns a locale, and the value LocalizationSettings.SelectedLocale falls back to. Setting it stores the locale's code; getting it resolves that code through LocalizationSettings.GetLocale, so the locale must be one of the LocalizationSettings.AvailableLocales.