added drink and snack

ps-grammar/gprs/gprs.jsgf

@@ -28,7 +28,7 @@ public <task> = [<robot_name>] [(would | could) you] [please] <command> [please]
 <personal_pronoun> = him | her | me;
 <person_name> = james|john|alfred|daniel|charles|luis|paul|richard|robert|steve|anna|beth|carmen|jennifer|jessica|kimberly|kristina|laura|mary|sarah;
 
-<grab_object> = <cleaning_class> | <drink_class> | <snack_class> | <food_class> | tool | (bathroom stuff) | cleaning_stuff | drinks | snacks | object | food | something | stuff | item | beverage | things;
+<grab_object> = <cleaning_class> | <drink_class> | <snack_class> | <food_class> | tool | (bathroom stuff) | cleaning_stuff | drinks | drink | snack | snacks | object | food | something | stuff | item | beverage | things;
 <cleaning_class> = brush | detergent | shampoo | sponge | toothpaste;
 <drink_class> = (orange juice) | beer | cola | chocolate_milk | energy_drink | grape_juice | milk | water;
 <snack_class> = chocolate_cookies | chips | biscuits | bread | pringles | (strawberry cookies);