fix BranchUniversalObject.generateShortUrl typings to return Promise<{url}>
fix BranchUniversalObject.generateShortUrl typings to return Promise<{url}>

BranchMetrics/react-native-branch-deep-linking,BranchMetrics/react-native-branch-deep-linking,BranchMetrics/react-native-branch-deep-linking,BranchMetrics/react-native-branch-deep-linking