Add validation to proxy names

Related to https://www.huntr.dev/bounties/31-other-FalconChristmas/fpp/

www/js/fpp.js

@@ -6030,3 +6030,48 @@ function PreviewStatistics() {
     $('#statsPreviewPopup').fppDialog( "moveToTop" );
     $('#statsPreviewDiv').load('api/statistics/usage');
 }
+
+function isValidIpAddress(ip)
+{
+    if (ip == "") {
+        return false;
+    }
+    return /^(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$/.test(ip);
+}
+
+
+// Source: https://github.com/miguelmota/is-valid-hostname/blob/master/index.js
+// License MIT: https://raw.githubusercontent.com/miguelmota/is-valid-hostname/master/LICENSE
+function isValidHostname(value) {
+    if (typeof value !== 'string') return false
+
+    const validHostnameChars = /^[a-zA-Z0-9-.]{1,253}\.?$/g
+    if (!validHostnameChars.test(value)) {
+      return false
+    }
+
+    if (value.endsWith('.')) {
+      value = value.slice(0, value.length - 1)
+    }
+
+    if (value.length > 253) {
+      return false
+    }
+
+    const labels = value.split('.')
+
+    const isValid = labels.every(function (label) {
+      const validLabelChars = /^([a-zA-Z0-9-]+)$/g
+
+      const validLabel = (
+        validLabelChars.test(label) &&
+        label.length < 64 &&
+        !label.startsWith('-') &&
+        !label.endsWith('-')
+      )
+
+      return validLabel
+    })
+
+    return isValid
+  }