docs: add examples

packages/docs/docs/api-reference/form-props.md

@@ -122,6 +122,68 @@ render(
 );
 ```
 
+### `allOf`
+
+Optional enumerated flag controlling how empty defaults are populated when `allOf` schemas are provided, defaulting to `skipDefaults`:
+
+| Flag Value         | Description                                                                                  |
+| ------------------ | -------------------------------------------------------------------------------------------- |
+| `skipDefaults`     | Skip parsing defaults from `allOf` schemas                                                   |
+| `populateDefaults` | Generate default values for properties in the `allOf` schema including `if-then-else` syntax |
+
+```tsx
+import { RJSFSchema } from '@rjsf/utils';
+import validator from '@rjsf/validator-ajv8';
+
+const schema: RJSFSchema = {
+  title: 'Example',
+  type: 'object',
+  properties: {
+    animalInfo: {
+      properties: {
+        animal: {
+          type: 'string',
+          default: 'Cat',
+          enum: ['Cat', 'Fish'],
+        },
+      },
+      allOf: [
+        {
+          if: {
+            properties: {
+              animal: {
+                const: 'Cat',
+              },
+            },
+          },
+          then: {
+            properties: {
+              food: {
+                type: 'string',
+                default: 'meat',
+                enum: ['meat', 'grass', 'fish'],
+              },
+            },
+            required: ['food'],
+          },
+        },
+      ],
+    },
+  },
+};
+
+render(
+  <Form
+    schema={schema}
+    validator={validator}
+    experimental_defaultFormStateBehavior={{
+      allOf: 'populateDefaults',
+    }}
+  />,
+  document.getElementById('app')
+);
+```
+
 ## disabled
 
 It's possible to disable the whole form by setting the `disabled` prop. The `disabled` prop is then forwarded down to each field of the form.