add formula to calculate pip speed

not used yet, but will be used eventually

src/app/shipyard/Calculations.js

@@ -86,6 +86,16 @@ export function speed(mass, baseSpeed, thrusters, engpip) {
   return results;
 }
 
+/**
+ * Calculate pip multiplier for speed.
+ * @param {number} topSpeed The top speed of ship in data
+ * @param {number} baseSpeed The base speed of ship in data
+ * @return {number} The multiplier that pips affect speed.
+ */
+export function calcPipSpeed(topSpeed, baseSpeed) {
+  return 1 - ((topSpeed - ((topSpeed - baseSpeed) / 4)) / topSpeed);
+}
+
 /**
  * Calculate pitch of a ship based on mass and thrusters
  * @param {number}   mass       the mass of the ship