move rarankToABC into a different file

src/models/rank-to-abc.ts

+
+
+
+export default function (rank: number, total: number) 
+{
+    rank /= total;
+    if (rank <= 0.01) return "A*";
+    if (rank <= 0.05) return "A";
+    if (rank <= 0.25) return "B";
+    return "C";
+}