feat: add a canGoBack prop to header back button

packages/stack/src/types.tsx

@@ -140,6 +140,7 @@ export type HeaderBackButtonProps = {
   onLabelLayout?: (e: LayoutChangeEvent) => void;
   screenLayout?: Layout;
   titleLayout?: Layout;
+  canGoBack?: boolean;
 };
 
 export type HeaderTitleProps = {

packages/stack/src/views/Header/HeaderSegment.tsx

@@ -313,6 +313,7 @@ export default class HeaderSegment extends React.Component<Props, State> {
                   screenLayout: layout,
                   titleLayout,
                   tintColor: headerTintColor,
+                  canGoBack: Boolean(onGoBack),
                 })}
               </Animated.View>
             ) : null}