add note for MS OS 1.0 Descriptor at 0xEE

examples/device/usbtmc/src/usb_descriptors.c

@@ -166,7 +166,8 @@ uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
   }
   else
   {
-    // Convert ASCII string into UTF-16
+    // Note: the 0xEE index string is a Microsoft OS 1.0 Descriptors.
+    // https://docs.microsoft.com/en-us/windows-hardware/drivers/usbcon/microsoft-defined-usb-descriptors
 
     if ( !(index < sizeof(string_desc_arr)/sizeof(string_desc_arr[0])) ) return NULL;
 
@@ -178,6 +179,7 @@ uint16_t const* tud_descriptor_string_cb(uint8_t index, uint16_t langid)
       chr_count = 31;
     }
 
+    // Convert ASCII string into UTF-16
     for(uint8_t i=0; i<chr_count; i++)
     {
       _desc_str[1+i] = str[i];