chore: add multibuild

Author: henryiii

source/key_projects.rst

@@ -55,9 +55,8 @@ cibuildwheel
 `Discussions <https://github.com/pypa/cibuildwheel/discussions>`__ |
 `Discord #cibuildwheel <https://discord.com/invite/pypa>`__
 
-``cibuildwheel`` is a package that builds wheels for all common platforms and
-Python versions on most CI systems.
-
+``cibuildwheel`` is a Python package that builds wheels for all common
+platforms and Python versions on most CI systems. Also see :ref:`multibuild`.
 
 .. _distlib:
 
@@ -458,6 +457,16 @@ dependencies for, and publish packages to PyPI. Under the hood, it
 uses :ref:`twine` to upload packages to PyPI, and :ref:`pip` to download and
 install packages.
 
+.. _multibuild:
+
+multibuild
+==========
+
+`GitHub <https://github.com/matthew-brett/multibuild>`__
+
+Multibuild is a set of CI scripts for building and testing Python Wheels for
+Linux, macOS, and (less flexibly) Windows. Also see :ref:`cibuildwheel`.
+
 .. _pex:
 
 pex