Add a comment about the SYS_NICE capability in start-docker

docker/start-docker

@@ -1,5 +1,8 @@
 #!/bin/bash
 
+# The SYS_NICE capability allows you to use numactl to pin processes to
+# NUMA nodes and/or individual cores
+
 docker run -d --cap-add SYS_NICE --rm --name prac_p0 -h prac_p0 -t prac
 docker run -d --cap-add SYS_NICE --rm --name prac_p1 -h prac_p1 -t prac
 docker run -d --cap-add SYS_NICE --rm --name prac_p2 -h prac_p2 -t prac