feat: 자율턴 한계 표기

hwe/ts/util/joinYearMonth.ts

@@ -0,0 +1,3 @@
+export function joinYearMonth(year: number, month: number): number {
+    return year * 12 + month - 1;
+}

hwe/ts/util/parseYearMonth.ts

@@ -0,0 +1,3 @@
+export function parseYearMonth(yearMonth: number): [number, number] {
+    return [(yearMonth / 12) | 0, yearMonth % 12 + 1];
+}