Update description

Provide link, like serviceHostingCountry

Signed-off-by: Arthit Suriyawongkul <arthit@gmail.com>

Author: bact

model/Core/Properties/inLanguage.md

@@ -8,8 +8,11 @@ Specifies a human language used within the content of an Element or a property.
 
 ## Description
 
-This property uses an IETF BCP 47 language tag to indicate a human language
-used within the content of an Element or a property.
+Specifies a human language used within the content of an Element or a property.
+
+The property value shall be an
+[IETF BCP 47 language tag](https://datatracker.ietf.org/doc/rfc5646/)
+used to indicating human languages, dialects, scripts, regions, and variants.
 
 ## Metadata