CSharpier - add way to show which files were formatted.

[belav]

There is currently no way to know which files csharpier formatted. For cases like #631 it would be useful to know which files were included.

Some ideas

1. --list-formatted could be used to only output the list of formatted files. That could then be piped to something else
2. output the formatted file + time as an Info level log and add an option for --loglevel