New port: editors/mle: Small, flexible, terminal-based text editor

mle is a small, flexible, terminal-based text editor written in C.
Notable features include: full Unicode support, syntax highlighting,
scriptable rc file, macros, search and replace (PCRE), window
splitting, multiple cursors, and integration with various shell
commands.

WWW: https://github.com/adsr/mle

PR: 240523
Submitted by: as@php.net
Differential Revision: https://reviews.freebsd.org/D21689
Event: EuroBSDcon 2019