editors/vis: New port: Vi-like editor based on Plan 9's structural regular expressions

Vis aims to be a modern, legacy-free, simple yet efficient editor,
combining the strengths of both vi(m) and sam.

It extends vi's modal editing with built-in support for multiple
cursors/selections and combines it with sam's structural regular
expression based command language.

Efficient syntax highlighting is provided using Parsing Expression
Grammars, which can be conveniently expressed using Lua in the form
of LPeg.

The editor core is written in a reasonable amount of clean, modern
and legacy-free C code, enabling it to run in resource-constrained
environments. There is also a Lua API for in-process extensions.

Vis strives to be simple and focuses on its core task: efficient
text management. Clipboard and digraph handling as well as a fuzzy
file open dialog are all provided by independent utilities.

WWW: https://www.brain-dump.org/projects/vis/

PR:	270063