Add annotations and labels to the Spec.

Signed-off-by: Vishnu kannan <vishnuk@google.com>

config.go

@@ -18,6 +18,8 @@ type Spec struct {
 	Mounts []Mount `json:"mounts"`
 	// Hooks are the commands run at various lifecycle events of the container.
 	Hooks Hooks `json:"hooks"`
+	// Annotations is an unstructured key value map that may be set by external tools to store and retrieve arbitrary metadata.
+	Annotations map[string]string `json:"annotations,omitempty"`
 }
 
 // Process contains information to start a specific application inside the container.

config.md

@@ -231,4 +231,17 @@ If a hook returns a non-zero exit code, then an error is logged and the remainin
 `args` and `env` are optional.
 The semantics are the same as `Path`, `Args` and `Env` in [golang Cmd](https://golang.org/pkg/os/exec/#Cmd).
 
+## Annotations
+
+Annotations are optional arbitrary non-identifying metadata that can be attached to containers.
+This information may be large, may be structured or unstructured.
+Annotations are key-value maps.
+
+```json
+"annotations": {
+	"key1" : "value1",
+	"key2" : "value2"
+}
+```
+
 [uts-namespace]: http://man7.org/linux/man-pages/man7/namespaces.7.html