Add self to people; 1st draft of mirage-tcpip post.

Comments and suggestions are very welcome.
I found this a bit confusing - it sounds like my application code is of type `stack impl`.
Other confusing things: there is also a type `stackv4 impl`, and `interface` here could mean an API or a network interface.

Perhaps something like "There are serveral Mirage functions that provide IPv4 stack implementations (`stackv4 impl`) ..."?