Player is now a Person

Use correct class inheritance, use class as type and remove IPlayer

src/PersonObjects/formulas/skill.ts

@@ -1,3 +1,7 @@
+/**
+ * Given an experience amount and stat multiplier, calculates the
+ * stat level. Stat-agnostic (same formula for every stat)
+ */
 export function calculateSkill(exp: number, mult = 1): number {
   return Math.max(Math.floor(mult * (32 * Math.log(exp + 534.5) - 200)), 1);
 }