WIP: Subscribe to resources

* In App.tsx
  - added subscribeToResource()
    - takes a uri
    - sends a `resources/subscribe` message with the uri
  - added unsubscribeFromResource()
    - takes a uri
    - sends a `resources/unsubscribe` message with the uri
  - in ResourcesTab element,
    - pass subscribeToResource and subscribeToResource invokers to component
* In notificationTypes.ts
  - add ServerNotificationSchema to NotificationSchema to permit server update messages.

* In ResourcesTab.tsx
  - deconstruct subscribeToResource and unsubscribeFromResource and add prop types
  - Add Subscribe and Unsubscribe buttons to selected resource panel, left of the refresh button. They call the sub and unsub functions that came in on props, passing the selected resource URI.
  - [WIP]: Will show the appropriate button in a follow up commit.
* In useConnection.ts
  - import ResourceUpdatedNotificationSchema
  - in the connect function,
    - set onNotification as the handler for ResourceUpdatedNotificationSchema

client/src/lib/hooks/useConnection.ts

@@ -9,6 +9,7 @@ import {
   CreateMessageRequestSchema,
   ListRootsRequestSchema,
   ProgressNotificationSchema,
+  ResourceUpdatedNotificationSchema,
   Request,
   Result,
   ServerCapabilities,
@@ -247,6 +248,11 @@ export function useConnection({
           ProgressNotificationSchema,
           onNotification,
         );
+
+        client.setNotificationHandler(
+          ResourceUpdatedNotificationSchema,
+          onNotification,
+        );
       }
 
       if (onStdErrNotification) {