js: add stretchInset in image

doric-js/index.d.ts

@@ -486,6 +486,18 @@ declare module 'doric/lib/src/widget/image' {
                     width: number;
                     height: number;
             } | undefined) => void;
+            /**
+                * Stretch a image according to pointed rect
+                * Rect contains left, top, right & bottom
+                * For Android, it is based on nine patch
+                * For iOS, it is based on cap insets & stretch mode
+                */
+            stretchInset?: {
+                    left: number;
+                    top: number;
+                    right: number;
+                    bottom: number;
+            };
     }
     export function image(config: Partial<Image>): Image;
 }