Fill in serial field for all HID controllers using hidapi

Controllers/LogitechController/LogitechG810Controller.cpp

@@ -21,6 +21,17 @@ LogitechG810Controller::~LogitechG810Controller()
 
 }
 
+std::string LogitechG810Controller::GetSerialString()
+{
+    wchar_t serial_string[128];
+    hid_get_serial_number_string(dev_pkt_0x11, serial_string, 128);
+
+    std::wstring return_wstring = serial_string;
+    std::string return_string(return_wstring.begin(), return_wstring.end());
+
+    return(return_string);
+}
+
 void LogitechG810Controller::Commit()
 {
     SendCommit();