Update mutually recursive record definition example (#27648)

It's incomplete without this change :)

Author: cartermp

docs/fsharp/language-reference/records.md

@@ -2,7 +2,7 @@
 title: Records in F#
 titleSuffix: ""
 description: Learn how F# records represent simple aggregates of named values, optionally with members.
-ms.date: 08/15/2020
+ms.date: 12/21/2021
 ---
 # Records (F#)
 
@@ -107,6 +107,24 @@ and Address =
     Occupant: Person }
 ```
 
+To create instances of both, you do the following:
+
+```fsharp
+// Create a Person type and use the Address type that is not defined
+let rec person =
+  {
+      Name = "Person name"
+      Age = 12
+      Address =
+          {
+              Line1 = "line 1"
+              Line2 = "line 2"
+              PostCode = "abc123"
+              Occupant = person
+          }
+  }
+```
+
 If you were to define the previous example without the `and` keyword, then it would not compile. The `and` keyword is required for mutually recursive definitions.
 
 ## Pattern Matching with Records