update issue template

Author: ROBOTIS-Will

.github/ISSUE_TEMPLATE.md

@@ -8,12 +8,17 @@ Please fill this template for more accurate and prompt support.
 2. Which programming language/tool do you use?
   - ex) `C`, `C++`, `C#`, `Python`, `Java`, `MATLAB`, `LABVIEW`, `ROS`, `Arduino`, etc
 
+3. Which operating system do you use?
+  - ex) `Ubuntu 16.04`, `Windows 10`, `OS X 10.14`
+
 3. Which USB serial converter do you use?
   - ex) `USB2Dynamixel`, `U2D2`, `OpenCM904`, `OpenCR`, etc
 
 4. Which DYNAMIXEL do you use?
   - ex) `MX-28(2.0)`, `AX-12W`, `XM430-W250`, etc.
 
-5. Please describe the issue in detail
+5. Have you searched the issue from the closed issue threads?
+
+6. Please describe the issue in detail
 
-6. How can we reproduce the issue?
+7. How can we reproduce the issue?