updated contributing guidelines [ci skip]
updated contributing guidelines [ci skip]

aiueogawa/ccxt,thijstriemstra/ccxt,thijstriemstra/ccxt,thijstriemstra/ccxt,tritoanst/ccxt,ccxt/ccxt,ccxt/ccxt,aiueogawa/ccxt,aiueogawa/ccxt,tritoanst/ccxt,aiueogawa/ccxt,tritoanst/ccxt,ccxt/ccxt,tritoanst/ccxt,ccxt/ccxt,ccxt/ccxt,thijstriemstra/ccxt