separate contributors, add new contributions

Author: imcelroy

CONTRIBUTORS.md

@@ -1,6 +1,6 @@
 # rclnodejs contributors (sorted alphabetically)
 
-- **[Alaa El Jawad](https://github.com/ejalaa12), [Ian McElroy](https://github.com/imcelroy)**
+- **[Alaa El Jawad](https://github.com/ejalaa12)**
 
   - Fix compatibility with ROS2 parameters array types
   - Unit tests for all parameter types
@@ -20,6 +20,13 @@
 
   - Benchmark test script
 
+- **[Ian McElroy](https://github.com/imcelroy)**
+
+  - Add descriptor namespace for all interfaces, rostsd_gen improvements
+  - Fix compatibility with ROS2 parameters array types
+  - Unit tests for all parameter types
+  - Handle concurrent ROS2 client calls, with unit tests
+
 - **[Kenny Yuan](https://github.com/kenny-y)**
 
   - Message features: JS generation, typed arrays, plain JS object, compound msgs, many others...