Add py38 package metadata

Change-Id: I1efa783233a435b6dbe134e035e0c2efb8ac1a6d
diff --git a/setup.cfg b/setup.cfg
index ec9e3ce..08441fa 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -17,6 +17,7 @@
     Programming Language :: Python :: 3
     Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7
+    Programming Language :: Python :: 3.8
 
 [files]
 packages =