fix: use correct callback type allowing for undefined i (#239)

src/types.ts

@@ -4,7 +4,7 @@ import { TextStyle, ViewStyle } from 'react-native';
 export interface ActionSheetProps {
   showActionSheetWithOptions: (
     options: ActionSheetOptions,
-    callback: (i: number) => void | Promise<void>
+    callback: (i?: number) => void | Promise<void>
   ) => void;
 }