This is a work-in-progress, but it is working thus far. It has most of the
built-in types, classes and interfaces, although it needs tweaking. It's based
around php.lua from Textadept's core lexer set, tweaked to handle Hack
better.
To install, copy lexers/hack.lua into your ~/.textadept/lexers/ folder
(create it if required). Then, open up ~/.textadept/properties.lua (again,
create it if need be) and copy the contents of the properties.lua in this
repository into it.
You'll need to change into Hack mode (Ctrl+Shift+L), as it defaults to PHP
for files that have the .php extension (.hh is fine though!).
See LICENSE.md.