contrib/python-zstandard/MANIFEST.in

dirstate-item: implement `added` in a simpler way

We can simply use the underlying attribute.

Differential Revision: https://phab.mercurial-scm.org/D11366

graft c-ext
graft debian
graft zstd
graft tests
include make_cffi.py
include setup_zstd.py
include zstd.c
include LICENSE
include NEWS.rst