Use wee-alloc as default allocator when feature is used

@@ -4,6 +4,14 @@ mod error;
 mod client;
 mod component;
 
+use cfg_if::cfg_if;
+cfg_if! {
+    if #[cfg(feature = "wee_alloc")] {
+        #[global_allocator]
+        static ALLOC: wee_alloc::WeeAlloc = wee_alloc::WeeAlloc::INIT;
+    }
+}
+
 #[cfg(feature = "console_error_panic_hook")]
 use std::panic;