minor update to webusb serial example

examples/device/webusb_serial/src/main.c

@@ -71,7 +71,7 @@ enum  {
 
 static uint32_t blink_interval_ms = BLINK_NOT_MOUNTED;
 
-#define URL  "example.tinyusb.org/webusb-serial/"
+#define URL  "example.tinyusb.org/webusb-serial/index.html"
 
 const tusb_desc_webusb_url_t desc_url =
 {
@@ -114,6 +114,7 @@ void echo_all(uint8_t buf[], uint32_t count)
   if ( web_serial_connected )
   {
     tud_vendor_write(buf, count);
+    tud_vendor_flush();
   }
 
   // echo to cdc
@@ -211,7 +212,8 @@ bool tud_vendor_control_xfer_cb(uint8_t rhport, uint8_t stage, tusb_control_requ
           board_led_write(true);
           blink_interval_ms = BLINK_ALWAYS_ON;
 
-          tud_vendor_write_str("\r\nTinyUSB WebUSB device example\r\n");
+          tud_vendor_write_str("\r\nWebUSB interface connected\r\n");
+          tud_vendor_flush();
         }else
         {
           blink_interval_ms = BLINK_MOUNTED;