Channel Export

Feature

• Channel export #504
• New event notification.invite_rejected #467
• Channel stopTyping accepts optional parent_id for typing in threads notification.invite_rejected #505

Fix

• Mute users no longer counted in channel unread #498
• AppSettingsAPIResponse type includes image_moderation_enabled #497
• User ban function signature updated #502:
  client.banUser('user1', {user_id: 'user2'}) is replaced with client.banUser('user1', {banned_by_id: 'user2'})