readme: mention fizzy-wasi

README.md

@@ -40,6 +40,20 @@ $ cmake --build .
 This will build Fizzy as a library and since there is no public API
 (the so called *embedder API* in WebAssembly) yet, this is not very useful.
 
+## WASI
+
+Building with the `FIZZY_WASI` option will output a `fizzy-wasi` binary implementing
+the [WASI] API (`wasi_snapshot_preview1` to be precise). It uses [uvwasi] under the hood.
+This can be used to execute WASI-compatible binaries on the command line.
+
+```sh
+$ mkdir build && cd build
+$ cmake -DFIZZY_WASI=ON ..
+$ cmake --build .
+```
+
+## Testing tools
+
 Building with the `FIZZY_TESTING` option will output a few useful utilities:
 
 ```sh
@@ -76,15 +90,18 @@ This is the unit tests suite of Fizzy.
 
 Licensed under the [Apache License, Version 2.0].
 
-[webassembly]: https://webassembly.org/
+[webassembly]: https://webassembly.org
 [standard readme]: https://github.com/RichardLitt/standard-readme
 [circleci]: https://circleci.com/gh/wasmx/fizzy/tree/master
-[codecov]: https://codecov.io/gh/wasmx/fizzy/
+[codecov]: https://codecov.io/gh/wasmx/fizzy
 [Apache License, Version 2.0]: LICENSE
 [@axic]: https://github.com/axic
 [@chfast]: https://github.com/chfast
 [@gumb0]: https://github.com/gumb0
 
+[WASI]: https://github.com/WebAssembly/WASI
+[uvwasi]: https://github.com/cjihrig/uvwasi
+
 [webassembly badge]: https://img.shields.io/badge/WebAssembly-Engine-informational.svg?logo=webassembly
 [readme style standard badge]: https://img.shields.io/badge/readme%20style-standard-brightgreen.svg
 [circleci badge]: https://img.shields.io/circleci/project/github/wasmx/fizzy/master.svg?logo=circleci