fix: export promoteChannel (#1474)

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## Description of the changes, What, Why and How?

Angular SDK needs to `setChannels` in case of
- reselecting previous active channel after reconnect
- `addChannel`, `removeChannel` methods

## Changelog

-

Author: szuperaz

src/index.ts

@@ -21,4 +21,4 @@ export * from './thread_manager';
 export * from './token_manager';
 export * from './types';
 export * from './channel_manager';
-export { isOwnUser, chatCodes, logChatPromiseExecution, formatMessage } from './utils';
+export { isOwnUser, chatCodes, logChatPromiseExecution, formatMessage, promoteChannel } from './utils';