Exports a function mergeFolders which allows you to specify to folders which should be merged into one.
The function will move each file for toMerge into target where no equivalent file exists. If both have the same file, it will compute a SHA-256 hash for each file's content to check if they're the same. If not, it will keep the file in toMerge for manual resolution.
Finally, it will clean up the toMerge directory removing any empty subdirectories including itself if no files has conflicts.