Files in one folder

Write a function filesInFolder(paths, folder) that returns the names of the files that are right in one folder.

• paths is an array of file paths of a project, like the output of git ls-files: folder names and the file name joined with /, for example 'src/utils/math.js'. A path never starts with /. The same path can occur more than once.
• folder is a string: a folder path from the project root, such as 'src' or 'src/utils'. 'src/' (with a slash at the end) means the same as 'src'. The empty string '' means the project root.
• Return an array of file names (the last part of a path, without folders). Take only files that are right in folder, not files in its subfolders. 'src2' is a different folder from 'src'.
• Every name is in the result once.
• Sort the names with the default sort(): it compares strings by character codes, so 'README.md' comes before 'app.js'.
• If no file is right in folder (also when there is no such folder or paths is empty), return an empty array.

You can split a path by / to get its parts.