bpo-22865: Expand on documentation for the pty.spawn function (GH-11980)

diff --git a/Misc/ACKS b/Misc/ACKS
index 77f1990..f9d01d0 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1859,3 +1859,4 @@
 Carsten Klein
 Diego Rojas
 Edison Abahurire
+Geoff Shannon