Add labels to the state

`Labels` is used to store some runtime specified informations,
these informations may be meaningless to other runtime, but it's
userful for the same runtime to operate this container.

Signed-off-by: Gao feng <[email protected]>

Author: gao-feng

config.go

@@ -67,4 +67,6 @@ type State struct {
 	Pid int `json:"pid"`
 	// Root is the path to the container's bundle directory.
 	Root string `json:"root"`
+	// Lables is the runtime itself specified information.
+	Labels map[string]string `json:"labels"`
 }

runtime.md

@@ -13,6 +13,7 @@ By providing a default location that container state is stored external applicat
 * **id** (string) ID is the container's ID.
 * **pid** (int) Pid is the ID of the main process within the container.
 * **root** (string) Root is the path to the container's bundle directory.
+* **Labels** (map) Labels is the runtime itself specified information.
 
 The ID is provided in the state because hooks will be executed with the state as the payload.
 This allows the hook to perform clean and teardown logic after the runtime destroys its own state.