T6406: document cpu limit config option

Author: nvollmar

docs/configuration/container/index.rst

@@ -133,6 +133,13 @@ Configuration
    - **always**: Restart containers when they exit, regardless of status,
      retrying indefinitely
 
+.. cfgcmd:: set container name <name> cpus <cores>
+
+   Constrain the cpu cores available to the container.
+
+   Default is 0 for unlimited.
+   This can be a decimal number with up to three decimal places.
+
 .. cfgcmd:: set container name <name> memory <MB>
 
    Constrain the memory available to the container.