add safe_duration_factor and safe_duration_offset to trip schema

Author: davidgamez

main/src/main/java/org/mobilitydata/gtfsvalidator/table/GtfsTripSchema.java

@@ -60,4 +60,8 @@ public interface GtfsTripSchema extends GtfsEntity {
   GtfsBikesAllowed bikesAllowed();
 
   GtfsCarsAllowed carsAllowed();
+
+  double safeDurationFactor();
+
+  double safeDurationOffset();
 }