Add agenda items for 04-08 meeting

Author: linclark

meetings/2021/WASI-04-08.md

@@ -28,4 +28,6 @@ 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. Phase 4 advancement requirements for current Phase 2 projects (Lin Clark)
+    2. Blockers for advancing wasi-filesystem to Phase 3 (Lin Clark)
+    3. Updates on wasi-io, with discussion of [Short reads versus determinism](https://github.com/WebAssembly/wasi-io/issues/7) and [What is a push?](https://github.com/WebAssembly/wasi-io/issues/9) (Dan Gohman)