Update runtime.md

Add an explicit explanation of the hooks order.
 
Signed-off-by: Liang Chenye <[email protected]>

Author: liangchenye

runtime.md

@@ -50,6 +50,7 @@ This event needs to be captured by runc to run onstop event handlers.
 ## Hooks
 
 Hooks allow one to run code before/after various lifecycle events of the container.
+Hooks MUST be called in the listed order.
 The state of the container is passed to the hooks over stdin, so the hooks could get the information they need to do their work.
 
 Hook paths are absolute and are executed from the host's filesystem.