prune files using the proper interface, rather than modifying the arrayref directly
Credit Karen Etheridge for github#19
Git::Commit: Ensure add_files_in is an ArrayRef[Path] to force validation at initialization
Role::Git::DirtyFiles : use Paths type for allow_dirty
Credit Kent Fredric for github#18
Coerce allow_dirty to Paths
Handle "allow_dirty =" as documented
v2.022

 - use MX:Path::Tiny Paths type to catch config issues at startup
   (kent fredric - github#18 & christopher madsen)
 - prune files using the prune_file method (karen etheridge - github#19)