fix(core): export NetworkConfigBuilder class (#345)

The `NetworkConfigBuilder` class, a key component of the new network
configuration API, was missing from the main exports. This class enables
users to customize network configurations with a fluent builder pattern.

packages/use-wallet/src/index.ts

@@ -1,6 +1,12 @@
 export { LogLevel } from './logger'
 export { WalletManager, WalletManagerConfig, WalletManagerOptions } from './manager'
-export { AlgodConfig, NetworkConfig, NetworkId, DEFAULT_NETWORK_CONFIG } from './network'
+export {
+  AlgodConfig,
+  NetworkConfig,
+  NetworkConfigBuilder,
+  NetworkId,
+  DEFAULT_NETWORK_CONFIG
+} from './network'
 export { State, WalletState, ManagerStatus, DEFAULT_STATE } from './store'
 export { StorageAdapter } from './storage'
 export { webpackFallback } from './webpack'