add image cache

desktop/src/main.rs

@@ -22,6 +22,10 @@ fn main() {
             // Initialize theme
             theme::init(cx);
 
+            // Install the shared image cache so avatars can be freed when
+            // their views close, instead of staying in memory forever.
+            workspace::image_cache::init(cx);
+
             // Initialize backend and stores (connects relays, restores session)
             std::fs::create_dir_all(paths::nostr_dir()).ok();
             signed_state::init(paths::nostr_dir(), cx);