Update require.md

Author: koperagen

docs/StardustDocs/topics/require.md

@@ -3,7 +3,7 @@
 
 Throws an exception if the specified column is missing or its type is not subtype of `C`.
 From the compiler plugin perspective, a new column will appear in the compile-time schema as a result of this operation.
-The aim here is to help incrementally migrate workflows to extension properties API.
+The aim here is to help incrementally migrate workflows to [extension properties API](extensionPropertiesApi.md).
 
 Will work in compiler plugin starting from IntelliJ IDEA 2026.2 and Kotlin 2.4.0.
 
@@ -14,6 +14,11 @@ require { column }
 **Related operations**: [](cast.md), [](convertTo)
 
 ```kotlin
+// Before `require` extension property will not be resolved
+// peopleDf.select { name.firstName }
+
+// Require a column with a runtime check
 val df = peopleDf.require { "name"["firstName"]<String>() }
+// Use extension property after `require`
 val v: String = df.name.firstName[0]
 ```