DeepL: Fix single value translation

DeepL return type is polymorphic and returns a single value instead of
an array when given a single element array.

Thanks to @lukasbischof, @jesusalc, @schmijos

Fixes #363
Fixes #347

lib/i18n/tasks/translators/deepl_translator.rb

@@ -17,7 +17,12 @@ def initialize(*)
     protected
 
     def translate_values(list, from:, to:, **options)
-      DeepL.translate(list, to_deepl_compatible_locale(from), to_deepl_compatible_locale(to), options).map(&:text)
+      result = DeepL.translate(list, to_deepl_compatible_locale(from), to_deepl_compatible_locale(to), options).map(&:text)
+      if result.is_a?(DeepL::Resources::Text)
+        result.text
+      else
+        result.map(&:text)
+      end
     end
 
     def options_for_translate_values(**options)