Add "display only favorite contacts" option (or tab)

[petRUShka]

Feature description

One of the favorite features of Bettergram (discontinued at the moment) is "Favorite tab". It helps to focus on what you do and to don't distract yourself more than you want to be distracted (especially with minimized notifications options). Also they have some other useful tabs: groups, single contacts, channels.

P.S. Why is so important to have option to see only favorites and decrease distraction? Tristan Harris former Product Philosopher at Google has explained.

Feature check-list

• [x] It has been released in Bettergram: https://github.com/bettergram/bettergram
• [x] This feature doesn't violate the Telegram Terms of Service

[hobbit19]

https://github.com/Sea-n/tdesktop