fixed useConnection hook, made derivedWarnings more specific, fixed updating when internals change

packages/svelte/src/lib/hooks/useConnection.svelte.ts

@@ -0,0 +1,18 @@
+import { useStore } from '$lib/store';
+
+import type { ConnectionState } from '@xyflow/system';
+import { derivedWarning } from './derivedWarning.svelte';
+
+/**
+ * Hook for receiving the current connection.
+ *
+ * @public
+ * @returns current connection as a readable store
+ */
+export function useConnection(): ConnectionState {
+  if (process.env.NODE_ENV === 'development') {
+    derivedWarning('useConnection', true);
+  }
+
+  return useStore().connection;
+}