bpo-37160: Thread native ID NetBSD support (GH-13835)

diff --git a/Doc/library/_thread.rst b/Doc/library/_thread.rst
index 26568dc..5b4fcde 100644
--- a/Doc/library/_thread.rst
+++ b/Doc/library/_thread.rst
@@ -106,7 +106,7 @@
    Its value may be used to uniquely identify this particular thread system-wide
    (until the thread terminates, after which the value may be recycled by the OS).
 
-   .. availability:: Windows, FreeBSD, Linux, macOS, OpenBSD.
+   .. availability:: Windows, FreeBSD, Linux, macOS, OpenBSD, NetBSD.
 
    .. versionadded:: 3.8