add lec38 (gpu-mode#43)

Author: metascroy

README.md

@@ -159,4 +159,8 @@ The PMPP Book: [Programming Massively Parallel Processors: A Hands-on Approach](
 
 # Lecture 37: Introduction to SASS & GPU Microarchitecture
 - Speaker: [Arun Demeure](https://github.com/ademeure)
-- [Slides](lecture_037/)
+- [Slides](lecture_037/)
+
+# Lecture 38: Lowbit kernels for ARM CPU
+- Speaker: [Scott Roy](https://github.com/metascroy)
+- [Slides](lecture_038/)