packaging: add pygit2 to the py3 Windows installers
This is needed to be able to use the git extension.
The extension no longer complains about the library being not installed, but
`hg log -r .` on a repo that works in WSL yielded a TypeError:
...
File "mercurial.hg", line 188, in _peerorrepo
File "mercurial.localrepo", line 3224, in instance
File "mercurial.localrepo", line 623, in makelocalrepository
File "hgext.git", line 117, in _makestore
File "hgext.git", line 48, in __init__
TypeError: Repository unable to unpack backend.
Differential Revision: https://phab.mercurial-scm.org/D9405
Mercurial
=========
Mercurial is a fast, easy to use, distributed revision control tool
for software developers.
Basic install::
$ make # see install targets
$ make install # do a system-wide install
$ hg debuginstall # sanity-check setup
$ hg # see help
Running without installing::
$ make local # build for inplace usage
$ ./hg --version # should show the latest version
See https://mercurial-scm.org/ for detailed installation
instructions, platform-specific notes, and Mercurial user information.