create secondary-background-color class

...etchat-channel-settings/client/views/channelSettings.html

packages/rocketchat-emoji-custom/admin/adminEmoji.html

packages/rocketchat-theme/server/colors.less

packages/rocketchat-ui-admin/admin/adminInfo.html

packages/rocketchat-ui-admin/admin/rooms/adminRooms.html

packages/rocketchat-ui-admin/admin/users/adminUsers.html

packages/rocketchat-ui-message/message/messageDropdown.html

...ges/rocketchat-ui-message/message/popup/messagePopup.html

packages/rocketchat-ui-sidenav/side-nav/sideNav.html

packages/rocketchat-ui/views/app/room.html

packages/rocketchat-ui/views/app/spotlight/spotlight.html