Add missing VirtualizedList Imperative Types

Summary:
Adds some imperative VirtualizedList methods to the TS types which are documented on the website and are public enough. Also explicitly add `viewOffset` to `scrollToItem` since `scrollToItem` params are indefinite in flow and are passed to `scrollToIndex` (which supports the prop).

Changelog:
[General][Fixed] - Add missing VirtualizedList Imperative Types

Reviewed By: GijsWeterings

Differential Revision: D42047674

fbshipit-source-id: 60f7b35b049853d9fcb724918b3a0008a75ea573

Author: NickGerleman

Libraries/Lists/FlatList.d.ts

@@ -206,6 +206,7 @@ export class FlatList<ItemT = any> extends React.Component<
   scrollToItem: (params: {
     animated?: boolean | null | undefined;
     item: ItemT;
+    viewOffset?: number | undefined;
     viewPosition?: number | undefined;
   }) => void;
 

Libraries/Lists/FlatList.js

@@ -334,6 +334,7 @@ class FlatList<ItemT> extends React.PureComponent<Props<ItemT>, void> {
   scrollToItem(params: {
     animated?: ?boolean,
     item: ItemT,
+    viewOffset?: number,
     viewPosition?: number,
     ...
   }) {

Libraries/Lists/VirtualizedList.d.ts

@@ -11,7 +11,12 @@ import type * as React from 'react';
 import type {LayoutChangeEvent} from '../../types';
 import {StyleProp} from '../StyleSheet/StyleSheet';
 import {ViewStyle} from '../StyleSheet/StyleSheetTypes';
-import type {ScrollViewProps} from '../Components/ScrollView/ScrollView';
+import type {
+  ScrollResponderMixin,
+  ScrollView,
+  ScrollViewProps,
+} from '../Components/ScrollView/ScrollView';
+import type {View} from '../Components/View/View';
 
 export interface ViewToken {
   item: any;
@@ -98,6 +103,7 @@ export class VirtualizedList<ItemT> extends React.Component<
   scrollToItem: (params: {
     animated?: boolean | undefined;
     item: ItemT;
+    viewOffset?: number | undefined;
     viewPosition?: number | undefined;
   }) => void;
 
@@ -113,6 +119,13 @@ export class VirtualizedList<ItemT> extends React.Component<
   }) => void;
 
   recordInteraction: () => void;
+
+  getScrollRef: () =>
+    | React.ElementRef<typeof ScrollView>
+    | React.ElementRef<typeof View>
+    | null;
+
+  getScrollResponder: () => ScrollResponderMixin | null;
 }
 
 /**

Libraries/Lists/VirtualizedList.js

@@ -263,6 +263,7 @@ export default class VirtualizedList extends StateSafePureComponent<
   scrollToItem(params: {
     animated?: ?boolean,
     item: Item,
+    viewOffset?: number,
     viewPosition?: number,
     ...
   }) {