Insights dependency and documentation improvements (#9815)

docs/core/services/form-rendering.service.md

@@ -7,7 +7,7 @@ Last reviewed: 2018-11-20
 
 # [Form Rendering service](../../../lib/core/src/lib/form/services/form-rendering.service.ts "Defined in form-rendering.service.ts")
 
-Maps a form field type string onto the corresponding form [widget component](../../insights/components/widget.component.md) type.
+Maps a form field type string onto the corresponding form [widget component](widget.component.md) type.
 
 ## Class members
 

docs/core/services/widget.component.md

@@ -0,0 +1,42 @@
+# Widget Component
+
+Base class for all standard and custom form widgets. All widgets must extend this class.
+
+## Basic Usage
+
+```ts
+import { Component } from '@angular/core';
+import { WidgetComponent } from '@alfresco/adf-core';
+
+@Component({
+    selector: 'custom-editor',
+    template: `
+        <div style="color: red">Look, I'm a custom editor!</div>
+    `
+})
+export class CustomEditorComponent extends WidgetComponent {}
+```
+
+## Class members
+
+### Properties
+
+| Name  | Type  | Default value | Description |
+|-------|-------|---------------|-------------|
+| field | `any` |               | field.      |
+
+### Events
+
+| Name         | Type                | Description   |
+|--------------|---------------------|---------------|
+| fieldChanged | `EventEmitter<any>` | fieldChanged. |
+
+## Details
+
+The `WidgetComponent` is the base class for all standard and custom form widgets.
+See the [Form Extensibility and Customisation](../../user-guide/extensibility.md) page for full details about
+implementing custom widgets.
+
+## See also
+
+-   [Extensibility](../../user-guide/extensibility.md)