[Feature iOS only] API to check whether a file is excluded from backup, and set or unset it when necessary

[Yupeng-li]

Hi there,

We have a scenario to toggle isExcludedFromBackup on iOS to exclude or include a file from/to backup. We think this can be a part of react-native-fs, so we added a patch locally to include these two functions.

export const isExcludedFromBackupIOS: (filepath: string)=> Promise<boolean>;
export const setIsExcludedFromBackupIOS: (filepath: string, isExcludedFromBackup: boolean)=> Promise<void>;

We'd like to submit a PR if you agree. Please let me know your thoughts.

[birdofpreyru]

Good. A few thoughts out of my head:

• Make it OS independent — isExcludedFromBackup() / setIsExcludedFromBackup().
• We need to check if similar feature exists on Android / Windows. If yes, we need to support it (perhaps later), otherwise we should return some static results from these functions on Android / Windows that make sense for default behavior there.
• Perhaps, setIsExcludedFromBackup() should resolve to boolean flag, true if OS supports that, false if not (so that it is possible to call it on any OS without error, but there is a way to check whether it actually has effect or not).