[libglnx] README.md: Add note on contributing

[Colin Walters <walters src gnome org>]

commit bf4d1504a40cdb2b1a90ed2eb6366ec28e60bb68
Author: Colin Walters <walters verbum org>
Date:   Wed Dec 2 09:58:18 2015 -0500

    README.md: Add note on contributing

 README.md |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)
---
diff --git a/README.md b/README.md
index b1f492f..50a5f90 100644
--- a/README.md
+++ b/README.md
@@ -42,3 +42,12 @@ APIs not defined in GLib yet, such as `glnx_fd_close`.
 
 `gs_transfer_out_value` is replaced by `g_steal_pointer`.
 
+Contributing
+------------
+
+Currently there is not a Bugzilla product - one may be created
+in the future.  You can submit PRs against the Github mirror:
+
+https://github.com/GNOME/libglnx/pulls
+
+Or alternatively, email one of the maintainers directly.