It's cheaper to buy two single port ones though :(
I'm sure we'll see ones that can handle enough output for a computer + phone in the near future!
I do carry an Anker with one USB-C and four A for travel with my (USB-C) laptop(s).
While I am wishing... A USB-C hub (bus powered or from a PD input) with full speed USB-C ports, maybe 4-6, and an A or two for good measure.
I know this is supported in this google dual-port PD charger: https://store.google.com/gb/product/usb_c_dual_port_charger
There is an explanation on how the power budget is split in this post: https://plus.google.com/+BensonLeung/posts/8jmUYtJxAwX
Presumably other multi-port chargers also do similair things