docs(form): add fieldsModel doc

Author: dolymood

document/components/docs/en-US/form.md

@@ -441,13 +441,13 @@ CubeForm is a schema-based form generator component.
 
 ### Events
 
-| Event Name | Description | Parameters 1 | Parameters 2 |
-| - | - | - | - |
-| submit | Form submit, only trigged when the form's validation is ok. If only have sync validators, this event will not be prevented by default. If have async validators, this event will be prevented by default. | e - event | form model value |
-| reset | Form reset | e - event | - |
-| validate | Form validated | Properties: <br>{<br>validity,<br> valid,<br> invalid,<br> dirty,<br> firstInvalidFieldIndex<br>} | - |
-| valid | Form valid | Validity result | - |
-| invalid | Form invalid | Validity result | - |
+| Event Name | Description | Parameters 1 | Parameters 2 | Parameters 3 |
+| - | - | - | - | - |
+| submit | Form submit, only trigged when the form's validation is ok. If only have sync validators, this event will not be prevented by default. If have async validators, this event will be prevented by default. | e - event | form model value | form model value with only fields `modelKey`<sup>1.12.30+</sup> |
+| reset | Form reset | e - event | - | - |
+| validate | Form validated | Properties: <br>{<br>validity,<br> valid,<br> invalid,<br> dirty,<br> firstInvalidFieldIndex<br>} | - | - |
+| valid | Form valid | Validity result | - | - |
+| invalid | Form invalid | Validity result | - | - |
 
 - `validate` event parameters
 

document/components/docs/zh-CN/form.md

@@ -441,13 +441,13 @@
 
 ### 事件
 
-| 事件名 | 说明 | 参数1 | 参数2 |
-| - | - | - | - |
-| submit | 表单校验通过后触发此事件，如果只有同步校验，则不会阻止默认行为，而如果包含了异步校验，则默认就会阻止默认行为 | e - 事件对象 | model 值 |
-| reset | 表单重置事件 | e - 事件对象 | - |
-| validate | 表单校验事件 | 参数结构如下：<br>{<br>validity,<br> valid,<br> invalid,<br> dirty,<br> firstInvalidFieldIndex<br>} | - |
-| valid | 表单校验成功触发 | validity 校验结果 | - |
-| invalid | 表单校验失败触发 | validity 校验结果 | - |
+| 事件名 | 说明 | 参数1 | 参数2 | 参数3 |
+| - | - | - | - | - |
+| submit | 表单校验通过后触发此事件，如果只有同步校验，则不会阻止默认行为，而如果包含了异步校验，则默认就会阻止默认行为 | e - 事件对象 | model 值 | 只包含存在的字段的 model 值<sup>1.12.30+</sup> |
+| reset | 表单重置事件 | e - 事件对象 | - | - |
+| validate | 表单校验事件 | 参数结构如下：<br>{<br>validity,<br> valid,<br> invalid,<br> dirty,<br> firstInvalidFieldIndex<br>} | - | - |
+| valid | 表单校验成功触发 | validity 校验结果 | - | - |
+| invalid | 表单校验失败触发 | validity 校验结果 | - | - |
 
 - `validate` 事件的参数