[Documentation] Add GetBuiltInParameterGroupTypeId usage example to Readme and update Changelog.

Author: Nice3point

Changelog.md

@@ -231,6 +231,7 @@ This update focuses on improved API design through C# 14 extension methods synta
 - `typeId.GetValidUnits()`
 - `typeId.GetTypeCatalogStringForSpec()`
 - `typeId.GetTypeCatalogStringForUnit()`
+- `typeId.GetBuiltInParameterGroupTypeId()`
 - `typeId.DownloadCompanyName(Document)`
 - `typeId.DownloadCompanyName(Document, string)`
 - `typeId.DownloadParameterOptions()`

Readme.md

@@ -1355,6 +1355,12 @@ var isValid = specTypeId.IsValidUnit(unitTypeId);
 var builtInParameter = forgeId.GetBuiltInParameter();
 ```
 
+**GetBuiltInParameterGroupTypeId** gets the parameter group identifier corresponding to the given built-in parameter identifier.
+
+```csharp
+var builtInParameterGroup = forgeId.GetBuiltInParameterGroupTypeId();
+```
+
 **GetAllBuiltInParameters** gets the identifiers of all built-in parameters.
 
 ```csharp