Add a "CHRO" tab

[user451421541757324]

hckr news is a peculiar frontend that displays a chronological list of items that have made it onto the Hacker News homepage (thus it is different from ordering by new). I feel that this order is very "natural" and also makes Hackernews more readable.

CHRO (short for chronological) would be a new tab in Hacki that follows the order of hckr news.

An API is available here (used by hckrweb, a frontend for hckr news).

It would also be nice if it could be set as the default tab when opening the app.