Fix manually-checked chores un-checking on refresh

I forgot to account for saving the data on the frontend, so it was only
ever using whatever the last data passed to us from the backend was,
which only happens once on initial load.

MMM-chores.js

@@ -52,12 +52,8 @@ Module.register("MMM-chores", {
 
     socketNotificationReceived(notification, payload) {
         if (notification === "CHORES_DATA_READ") {
-            for (const v in payload) {
-                const elem = document.getElementById(v)
-                if (elem) {
-                    elem.checked = payload[v] === 1
-                }
-            }
+            this.saved_data = payload
+            this.updateDom()
         }
     },
 
@@ -83,9 +79,14 @@ Module.register("MMM-chores", {
         if (id !== undefined) {
             cb.id = id
         }
+        cb.checked = this.saved_data && this.saved_data[cb.id] === 1
         cb.onclick = (ev) => {
             let targetId = ev.target.id
             let val = cb.checked ? 1 : 0
+            if (!this.saved_data) {
+                this.saved_data = {}
+            }
+            this.saved_data[targetId] = val
             this.sendSocketNotification("CHORES_ADD_DATA", { "key": targetId, "val": val })
 
             const numItems = 2