feat: add preloadItemCount for List, incase we need preload more items before scroll to end

doric-js/lib/src/widget/list.d.ts

@@ -49,6 +49,7 @@ export declare class List extends Superview {
     beforeDragging?: (from: number) => (Array<number> | void);
     onDragging?: (from: number, to: number) => void;
     onDragged?: (from: number, to: number) => void;
+    preloadItemCount?: number;
     scrollToItem(context: BridgeContext, index: number, config?: {
         animated?: boolean;
     }): Promise<any>;

doric-js/lib/src/widget/list.js

@@ -162,6 +162,10 @@ __decorate([
     Property,
     __metadata("design:type", Function)
 ], List.prototype, "onDragged", void 0);
+__decorate([
+    Property,
+    __metadata("design:type", Number)
+], List.prototype, "preloadItemCount", void 0);
 export function list(config) {
     const ret = new List;
     ret.apply(config);