Return a promise for getReferrerInfoAsync on web (#4777)

modules/expo-bluesky-swiss-army/src/Referrer/index.web.ts

@@ -7,7 +7,7 @@ export function getGooglePlayReferrerInfoAsync(): Promise<GooglePlayReferrerInfo
   throw new NotImplementedError()
 }
 
-export function getReferrerInfoAsync(): Promise<ReferrerInfo | null> {
+export async function getReferrerInfoAsync(): Promise<ReferrerInfo | null> {
   if (
     Platform.OS === 'web' &&
     // for ssr
@@ -29,6 +29,5 @@ export function getReferrerInfoAsync(): Promise<ReferrerInfo | null> {
       console.error('Failed to parse referrer URL')
     }
   }
-
   return null
 }