New port: editors/gomate

Gomate is an implementation of rmate in Go. It allows editing of
files via an ssh session in TextMate, VSCode, or any other editor
that supports rmate.

WWW: https://github.com/mattn/gomate

PR: 228486
Submitted by: Fabian Freyer <fabian.freyer@physik.tu-berlin.de>
Differential Revision: https://reviews.freebsd.org/D15573