Add items to 05-06 meeting agenda

Author: linclark

meetings/2021/WASI-05-06.md

@@ -28,4 +28,5 @@ The meeting will be on a zoom.us video conference.
 1. Announcements
     1. _Sumbit a PR to add your announcement here_
 1. Proposals and discussions
-    1. _Sumbit a PR to add your agenda item here_
+    1. Presentation: Supporting alternative ABIs for blocking function calls (Luke Wagner)
+    2. Demo (if time allows): Update on wasi-io (Dan Gohman)