load hashes from cache for checkpoints that have them

add checkpoint hash to footer

script.js

@@ -14,6 +14,7 @@ function get_uiCurrentTabContent() {
 
 uiUpdateCallbacks = []
 uiTabChangeCallbacks = []
+optionsChangedCallbacks = []
 let uiCurrentTab = null
 
 function onUiUpdate(callback){
@@ -22,6 +23,9 @@ function onUiUpdate(callback){
 function onUiTabChange(callback){
     uiTabChangeCallbacks.push(callback)
 }
+function onOptionsChanged(callback){
+    optionsChangedCallbacks.push(callback)
+}
 
 function runCallback(x, m){
     try {