fix: add isValidLatLngTuple function to validate latitude and longitude tuples

Author: graffkevin

src/types/isValidMarker.ts

@@ -14,6 +14,13 @@ export const isValidLongitude = (value: unknown): value is number => {
   return typeof value === "number" && value >= -180 && value <= 180;
 };
 
+/**
+ * Checks if value is a valid [latitude, longitude] tuple.
+ */
+export const isValidLatLngTuple = (value: unknown): value is [number, number] => {
+  return Array.isArray(value) && value.length === 2 && isValidLatitude(value[0]) && isValidLongitude(value[1]);
+};
+
 /**
  * Type guard that validates a MarkerProps object at runtime
  * and narrows lat/lng from unknown to number.