Add information about design property category

Author: hendrik-jacobs-mendix

content/en/docs/apidocs-mxsdk/apidocs/frontend/design-properties.md

@@ -61,6 +61,7 @@ Here is a simplified example of a design properties file:
             "name": "My Toggle Property",
             "type": "Toggle",
             "description": "Description of My Toggle Design Property",
+            "category": "Best place for this toggle property"
             "class": "hereMyClass"
         },
         {
@@ -111,14 +112,26 @@ Every design property in the array is also represented by a *JSON* object. The e
 
 #### Common Fields
 
-The examples above show that the fields `name` and `description` define the UI, the name of a form control in Studio Pro, and the description under it. They are required string values naming and describing a design property. 
+The common fields, as seen within the example above, are available on all the design properties as defined in the following table.
 
-Field `type` defines the type of a property and must be one of the design property types: `Toggle`, `Dropdown`, `Colorpicker`, `ToggleButtonGroup` or `Spacing`.
+
+| Field          | Required | Type   | Description                                                                                   |
+| -------------- | -------- | ------ | --------------------------------------------------------------------------------------------- |
+| `name`         | Yes      | String | The name and identifier for the design property, that will be displayed on the UI.            |
+| `description`  | Yes      | String | A short description of the design property and what it provides.                              |
+| `type`         | Yes      | String | Defines the type of a property .                                                              |
+| `category`     | No       | String | An identifier that will be used to group design properties on the UI (defaults to "General"). |
 
 {{% alert color="warning" %}}
 Name your design property and its options carefully. Those names cannot be changed easily when there are apps already using them. If you want to rename a design property which is already being used in an app, see the [Renaming Design Properties](#old-names) section below.
 {{% /alert %}}
 
+##### Limitations
+
+It is important to note that the `category` shouldn't be "Common" as this is a reserved category and will cause Studio Pro to raise a warning and display that design property within the default category.
+
+The `type`property must be one of the following design property types: `Toggle`, `Dropdown`, `Colorpicker`, `ToggleButtonGroup` or `Spacing`.
+
 #### Toggle-Specific Fields
 
 Design properties of type **Toggle** have the following additional field: