add some comments

packages/freesewing.shared/hooks/useLocalStorage.js

@@ -4,19 +4,22 @@ import { useState, useEffect } from 'react'
 function useLocalStorage(key, initialValue) {
   const prefix = 'fs_'
   const [storedValue, setStoredValue] = useState(initialValue);
+  // use this to track whether it's mounted. useful for doing other effects outside this hook
   const [ready, setReady] = useState(false);
 
   const setValue = (value) => {
-    if (typeof window === 'undefined') return null // SSR has no window object
+    if (!ready) return null
     try {
       const valueToStore = value instanceof Function ? value(storedValue) : value
       setStoredValue(valueToStore)
+
       window.localStorage.setItem(prefix + key, JSON.stringify(valueToStore))
     } catch (error) {
       console.log(error)
     }
   }
 
+  // get the item from localstorage after the component has mounted. empty brackets mean it runs one time
   useEffect(() => {
     const item = window.localStorage.getItem(prefix + key)
     if (item) {