games/star_traders: new port: text-based game

Star Traders is a simple text-based game of interstellar trading,
where the objective is to create companies, buy and sell shares,
borrow and repay money, in order to become the wealthiest player
(the winner).

WWW: https://www.zap.org.au/projects/trader/

PR:		278349
Approved by:	submitter is maintainer, diizzy (mentor)
Differential Revision:	https://reviews.freebsd.org/D45091