Support sticky headers for inverted Lists

Summary:
Sticky headers for inverted lists should still stick at the top of the list instead of the bottom.

Tested by adding the inverted prop to the SectionList example in RNTester.

It does add a prop to ScrollView but it's very specific to the inverted list implementation, not sure if it should be documented.

[GENERAL][ENHANCEMENT][LISTS] -  Support sticky headers for inverted Lists
Closes https://github.com/facebook/react-native/pull/17762

Differential Revision: D6830784

Pulled By: sahrens

fbshipit-source-id: 6841fdd46e04b30547659d85ff54c3a21c61a8a2

Libraries/Lists/VirtualizedList.js

@@ -898,6 +898,7 @@ class VirtualizedList extends React.PureComponent<Props, State> {
       onScrollEndDrag: this._onScrollEndDrag,
       onMomentumScrollEnd: this._onMomentumScrollEnd,
       scrollEventThrottle: this.props.scrollEventThrottle, // TODO: Android support
+      invertStickyHeaders: this.props.inverted,
       stickyHeaderIndices,
     };
     if (inversionStyle) {