Added frontend code for limits

www/main.js

@@ -1,3 +1,21 @@
+async function GET(path) {
+    return new Promise(function (onSuccess, onError) {
+        let xhr = new XMLHttpRequest();
+        xhr.open('GET', path);
+        xhr.onreadystatechange = function () {
+            if (xhr.readyState === 4) {
+                if (xhr.status === 200) {
+                    onSuccess(JSON.parse(xhr.responseText));
+                } else {
+                    onError(xhr);
+                }
+            }
+        }
+        xhr.onerror = () => onError(xhr);
+        xhr.send(null);
+    });
+}
+
 async function POST(path, data={}) {
     return new Promise(function (onSuccess, onError) {
         var xhr = new XMLHttpRequest();
@@ -57,3 +75,10 @@ async function vibrate() {
 async function beep() {
     txFromUI('beep');
 }
+
+window.addEventListener('load', () => {
+    GET('/limit').then((data) => {
+        document.getElementById('shockIntensity').max = data.limit;
+        document.getElementById('vibrateIntensity').max = data.limit;
+    });
+});