design update: List of Chats screen

[Taras Filatov]

List of Chats is to be updated according to the new design.

Notes:

• The default Tabs should be shown as follows: Favorites, Groups, Private
• Tabs should be centered / spaced out horizontally
• If pulled down, there should be a UI for Search and " + New Chat" button, as shown in 2nd set of screen designs below, the design assets will be updated with this.

[polipivnenko]

[Taras Filatov]

I think this looks good. Thank you @polipivnenko. Let's go ahead with implementation, @dzinzyura