schema: Add enumeration to rootfsPropagation values

Signed-off-by: zhouhao <[email protected]>

Author: zhouhao

schema/config-linux.json

@@ -227,7 +227,7 @@
             },
             "rootfsPropagation": {
                 "id": "https://opencontainers.org/schema/bundle/linux/rootfsPropagation",
-                "type": "string"
+                "$ref": "defs-linux.json#/definitions/RootfsPropagation"
             },
             "seccomp": {
                 "id": "https://opencontainers.org/schema/bundle/linux/seccomp",

schema/defs-linux.json

@@ -1,5 +1,14 @@
 {
     "definitions": {
+        "RootfsPropagation": {
+            "type": "string",
+            "enum": [
+                "private",
+                "shared",
+                "slave",
+                "unbindable"
+            ]
+        },
         "SeccompArch": {
             "type": "string",
             "enum": [