fix(zoomimage): typings fix

Author: farfromrefug

src/zoomimage/index-common.ts

@@ -3,10 +3,11 @@ import { Property } from '@nativescript/core';
 
 export { initialize };
 
-export class ZoomImageBase extends Img {
+export abstract class ZoomImageBase extends Img {
     zoomScale: number;
     minZoom: number;
     maxZoom: number;
+    abstract setZoom(scale: number, animated?: boolean, point?: { x; y });
 }
 
 export const zoomScaleProperty = new Property<ZoomImageBase, number>({

src/zoomimage/index.d.ts

@@ -1,3 +1,4 @@
-import { Img } from '@nativescript-community/ui-image';
+import { ZoomImageBase } from './index-common';
 
-export class ZoomImg extends Img {}
+export class ZoomImg extends ZoomImageBase {
+}