[docs] Add new sandbox feature to docs.
diff --git a/package_metadata.md b/package_metadata.md
index 4ff682d..6cf08b1 100644
@@ -90,4 +90,8 @@
`/system/data/boringssl` directories in the package's namespace. (The latter
of which will be removed once all clients transition to the former.)
+- `persistent-storage`, which requests access to persistent storage for the
+ device, located in `/data` in the package's namespace. (Future work will
+ likely make this access more fine-grained than just the `/data` directory.)
See [sandboxing.md](sandboxing.md) for more information about sandboxing.