Update CaptivePortal.ino (espressif#3628)

Small change to insure wifi starts off and avoid crashing

Author: DanielLester83

libraries/DNSServer/examples/CaptivePortal/CaptivePortal.ino

@@ -11,7 +11,9 @@ String responseHTML = ""
  "<h1>Hello World!</h1><p>This is a captive portal example. All requests will "
  "be redirected here.</p></body></html>";
 
-void setup() {
+void setup() { 
+ WiFi.disconnect(); //added to start with the wifi off, avoid crashing
+ WiFi.mode(WIFI_OFF); //added to start with the wifi off, avoid crashing
  WiFi.mode(WIFI_AP);
  WiFi.softAPConfig(apIP, apIP, IPAddress(255, 255, 255, 0));
  WiFi.softAP("DNSServer CaptivePortal example");