Update cache-field-behavior.md (#6755)

The official documentation lacked an example and description of how to
handle multiple parameters within the read() function when defining
typePolicies. The proposed change addresses that by both showcasing that
it is possible to handle multiple parameters and how to do so (using a
syntax that was previously undocumented).

I struggled for a while when it came to understanding how to handle this
use case, so I am more than happy to share my findings while improving
the docs with the hope of helping others that might find themselves in
the same situation. 😃

Author: Moristotle

docs/source/caching/cache-field-behavior.mdx

@@ -79,6 +79,43 @@ const cache = new InMemoryCache({
 });
 ```
 
+If a field requires numerous parameters then each parameter must be wrapped in a variable that is then destructured and returned.
+Each parameter will be available as individual subfields.
+
+The following `read` function assigns a default value of `UNKNOWN FIRST_NAME` to the `first_name` subfield of a `fullName` field and a `UNKNOWN LAST_NAME` to the `last_name` of a `fullName` field.
+
+```ts
+const cache = new InMemoryCache({
+  typePolicies: {
+    Person: {
+      fields: {
+        fullName: {
+          read(full_name = {
+            first_name: "UNKNOWN FIRST_NAME",
+            last_name: "UNKNOWN LAST_NAME",
+          }) {
+            return { ...full_name };
+          },
+        },
+      },
+    },
+  },
+});
+```
+
+The following `query` returns the `first_name` and `last_name` subfields from the `fullName` field:
+
+```graphql
+query personWithFullName {
+  fullName {
+    first_name
+    last_name
+  }
+}
+```
+
+If a field accepts arguments, the second parameter includes the values of those arguments. The following `read` function checks to see if the `maxLength` argument is provided when the `name` field is queried. If it is, the function returns only the first `maxLength` characters of the person's name. Otherwise, the person's full name is returned.
+
 You can define a `read` function for a field that isn't even defined in your schema. For example, the following `read` function enables you to query a `userId` field that is always populated with locally stored data:
 
 ```ts