✨ Add history view

src/store.js

@@ -1,8 +1,17 @@
 import { computed } from "@vue/reactivity";
 import { ref } from "vue";
 
-export const timetable = ref([]);
-export const substitutions = ref([]);
+export const history = ref([]);
+
+export const historyOfDate = computed(() => {
+  const dates = {};
+  for (const entry of history.value) {
+    const date = entry.date;
+    if (!dates[date]) dates[date] = [];
+    dates[entry.date].push(entry);
+  }
+  return dates;
+});
 
 export const substitutionsForDate = computed(() => {
   const dates = {};