config: add warnings for unspecified file/dir modes

When the mode is unspecified on a file or directory it defaults to 0.
Add warnings to inform users of this.

config/types/directory.go

@@ -26,5 +26,11 @@ func (d Directory) ValidateMode() report.Report {
 			Kind:    report.EntryError,
 		})
 	}
+	if d.Mode == nil {
+		r.Add(report.Entry{
+			Message: "directory permissions unset, defaulting to 0000",
+			Kind:    report.EntryWarning,
+		})
+	}
 	return r
 }

config/types/file.go

@@ -33,6 +33,12 @@ func (f File) ValidateMode() report.Report {
 			Kind:    report.EntryError,
 		})
 	}
+	if f.Mode == nil {
+		r.Add(report.Entry{
+			Message: "file permissions unset, defaulting to 0000",
+			Kind:    report.EntryWarning,
+		})
+	}
 	return r
 }