Rewrite README for WASI 0.2 branch

Author: ricochet

README.md

@@ -1,41 +1,25 @@
-<img width="100px" src="assets/WASI.png">
+# WASI 0.2 docs
 
-# WebAssembly System Interface
+This branch documents the WASI 0.2 iteration of WASI, also known as Preview 2.
 
-[![DOI](https://zenodo.org/badge/DOI/10.5281/zenodo.4323447.svg)](https://doi.org/10.5281/zenodo.4323447)
-    
+WASI 0.2 is a modular collection of APIs defined using the [Wit IDL]. It
+incorporates many of the lessons learned from [Preview 1], including support
+for a wider range of source languages, modularity, a more expressive type
+system, virtualizability, and more. It covers the `wasi:cli`, `wasi:clocks`,
+`wasi:filesystem`, `wasi:http`, `wasi:io`, `wasi:random`, and `wasi:sockets`
+interfaces at their 0.2.x versions.
 
-The WebAssembly System Interface (WASI) is a set of APIs for WASI being
-developed for eventual standardization by the WASI Subgroup, which is a
-subgroup of the WebAssembly Community Group.
+Development of WASI now continues in [WASI 0.3] (Preview 3) on the `main`
+branch, which supplants Preview 2 by providing integrated and composable
+`async` functionality. Implementations may continue to support WASI 0.2,
+either by implementing WASI 0.3 alongside it, or by virtualizing
+(polyfilling) 0.2 in terms of 0.3.
 
-WASI started with launching what is now called [Preview 1], an API using
-the witx IDL, and it is now widely used. Its major influences are POSIX and
-CloudABI.
-
-[WASI Preview 2] is now stable, and is a modular collection of
-APIs defined with the [Wit IDL], and it incorporates many of the lessons
-learned from Preview 1, including adding support for a wider range of
-source languages, modularity, a more expressive type system,
-virtualizability, and more.
+The proposals included in WASI 0.2 are documented under [`proposals/`](proposals),
+and the tagged interface snapshots are under [`specifications/`](specifications).
+See [Preview2.md](docs/Preview2.md) for the Preview 2 inclusion criteria and
+overview.
 
 [Preview 1]: https://github.com/WebAssembly/WASI/tree/wasi-0.1
-[WASI Preview 2]: https://github.com/WebAssembly/WASI/blob/main/docs/Preview2.md
+[WASI 0.3]: https://github.com/WebAssembly/WASI/tree/main
 [Wit IDL]: https://github.com/WebAssembly/component-model/blob/main/design/mvp/WIT.md
-
-## Find the APIs
-
-Development of each API happens in its own repo, which you can access
-from the [proposals list](docs/Proposals.md).
-
-This repo is for general discussion, as well as documenting how we work
-and high-level goals.
-
-## Propose a new API
-
-If you would like to create a new proposal, get started with our
-[Contributing guide](CONTRIBUTING.md).
-
-All new API proposals should use the new format and the new repo structure that is shown in the [proposal template](https://github.com/WebAssembly/wasi-proposal-template).
-
-See the [Wit in WASI](docs/WitInWasi.md) document for more information about using Wit for WASI proposals.