feat: add very short green multiplier for welsh scoring

Author: brownben

backend/src/utils/points_calculators.py

@@ -225,6 +225,7 @@ def get_multipliers(self, age_class: str, course_ran: str) -> int:
             "short blue": 0.7,
             "green": 0.6,
             "short green": 0.5,
+            "very short green": 0.5,
             "light green": 0.5,
             "orange": 0.37,
             "yellow": 0.3,