Allow the loading of a list of ignored paths from file

[mihai-dinculescu]

Currently one or more paths can be ignored by using the -i flag.

cargo wipe rust -i /home/user/path1 -i /home/user/path2

It would be most useful if these paths can be loaded from a file

cargo wipe rust -i /home/user/paths_to_ignore.txt

/home/user/paths_to_ignore.txt can contain one or more paths separated by new lines

/home/user/path1
/home/user/path2

This can be easily achieved by checking if the path given to the -i flag is a directory or a file.
If it's a directory, just ignore it. If it's a file, attempt to open it as text and parse the paths inside.