update readme with link to base16
update readme with link to base16

wangtingbang/spacegray,wengyulin/spacegray,qiuyesuifeng/spacegray,VANITAX/spacegray,mjrev/spacegray,ericmatthys/spacegray-oceanic-next,marcofugaro/spacegray,cmelbye/spacegray,pongstr/spacegray,jay3126/spacegray,markhuot/spacegray,mjrev/spacegray,mhkeller/spacegray,kkga/spacegray,lancevalour/spacegray,VikingDen/spacegray,mhkeller/spacegray,mjrev/spacegray,silverbux/spacegray