languagecode_criterion.md: highlighted lines, grammar

Author: adriendupuis

docs/search/criteria_reference/languagecode_criterion.md

@@ -49,8 +49,8 @@ into a specific language:
 ```
 
 You can use the `LanguageCode` Criterion to search in
-several languages while ensuring result have a translation in one language:
+several languages while ensuring results have a translation in one specific language:
 
-``` php
+``` php hl_lines="3 7"
 [[= include_file('code_samples/search/language/src/Command/SearchTestCommand.php', 35, 48) =]]
 ```