save custom msg to json file after clicking add

static/app.js

@@ -1600,8 +1600,8 @@ function getImageSettings(page) {
   return settings;
 }
 
+// ADD MSG TO LIST AND SAVE MSG TO JSON FILE
 var messages = [];
-
 messagesTextAddBtn.addEventListener("click", () => {
   let pageSelector = "Page13";
 
@@ -1624,6 +1624,11 @@ messagesTextAddBtn.addEventListener("click", () => {
     background_colour: background_colour,
   };
   messages.push(message);
+  
+  fetch("/sendMsgToJSON", {
+     method: "POST",
+     body: JSON.stringify(message),
+   });
 });
 
 function getMessageSettings(page) {