Add getLanguageWithFallback() to ConfigGroupMapper

+++ b/lib/Drupal/config_translation/ConfigGroupMapper.phpundefined
@@ -149,6 +149,22 @@ class ConfigGroupMapper implements ConfigMapperInterface {
+   * Returns the language of the configuration group, if there is no language
+   * found, returns a dummy English language
+   *

First comment should be 1 line.

Let's explain why do we do this :) Something like "If there is no language found and the original language code is 'en', we return a dummy English language to represent the built-in English language."

+++ b/lib/Drupal/config_translation/ConfigGroupMapper.phpundefined
@@ -149,6 +149,22 @@ class ConfigGroupMapper implements ConfigMapperInterface {
+   *   Language object with the language of the configuration group, or dummy
+   *   English fallback language if no language.
+   *

We can simplify this down to "A configured language object instance or a dummy English language object." Or something along those lines.

Thanks, committed! This will be useful in multiple issues!