FileUtil.CopyFileOrDirectory
static function CopyFileOrDirectory(from: string, to: string): void;
Description

Copies a file or a directory.

This function's path can be relative to the project root folder or be an absolute path.

All file separators should be forward ones "/".

Make sure to include the name of the files or directories at the end of the "to" argument.
    @MenuItem ("Example/Copy Something")
    static function CopyAFile () {
        // copies the file "YourFileOrFolder" from "path/" to "copypath"
        FileUtil.CopyFileOrDirectory ("path/YourFileOrFolder", "copypathYourFileOrFolder");
    }