Create a new folder with formatted number and custom name in the directory
set with path. If no path is given, the folder will be created in the
current working directory. The newly created folder will be labelled with the
number n + 1 with n being the number of folders already existent in the
working directory. If a folder with the same name (must not be the same
number) already exists, you can choose to add another one with the same name
(and different number).
Usage
use_custom_folder(folder_name, path = fs::path_wd(), add = FALSE)