doc: add more details for localStorage and sessionStorage

doc/api/globals.md

@@ -592,8 +592,11 @@ added: v22.4.0
 
 A browser-compatible implementation of [`localStorage`][]. Data is stored
 unencrypted in the file specified by the [`--localstorage-file`][] CLI flag.
+The maximum amount of data that can be stored is 10 MB.
 Any modification of this data outside of the Web Storage API is not supported.
 Enable this API with the [`--experimental-webstorage`][] CLI flag.
+`localStorage` data is not stored per user or per request when used in the context
+of a server, it is shared across all users and requests.
 
 ## `MessageChannel`
 
@@ -972,9 +975,11 @@ added: v22.4.0
 > Stability: 1.0 - Early development.
 
 A browser-compatible implementation of [`sessionStorage`][]. Data is stored in
-memory, with a storage quota of 10 MB. Any modification of this data outside of
-the Web Storage API is not supported. Enable this API with the
-[`--experimental-webstorage`][] CLI flag.
+memory, with a storage quota of 10 MB. `sessionStorage` data persists only within
+the currently running process, and is not shared between workers.
+[`--experimental-webstorage`][] CLI flag. `sessionStorage` data is not stored per
+user or per request when used in the context of a server, it is specific to
+a single context.
 
 ## `setImmediate(callback[, ...args])`