chore: Organize & index design docs (#515)

Author: jbelkins

design/README.md

@@ -0,0 +1,12 @@
+# smithy-swift Design Documents
+
+### Legacy docs: available [here](DESIGN.md)
+
+### Design template: available [here](rfc-00000-template.md)
+
+Designs are generally conceived, written and reviewed internally.
+Once a design is finalized, it will be published here for reference.
+
+### Design documents
+- [RFC-00001: Event streams](rfc-00001-event-stream.md)
+- [RFC-00002: Waiters](rfc-00002-waiters.md)

design/waiters.md renamed to design/rfc-00002-waiters.md

@@ -1,4 +1,8 @@
-# Waiters Design
+# Waiters
+
+* Proposal: **RFC-00002**
+* Author: [Josh Elkins](https://github.com/jbelkins)
+* Status: **Implemented**
 
 ## Introduction