update README.md

Author: kateinoigakukun

README.md

@@ -1,6 +1,6 @@
 # μWASI
 
-This library provides a WASI implementation in a tree-shaking friendly way.
+This library provides a WASI implementation for Node.js and browsers in a tree-shaking friendly way.
 The system calls provided by this library are configurable.
 
 With minimal configuration, it provides WASI system calls which just return `WASI_ENOSYS`.
@@ -59,3 +59,18 @@ const wasi = new WASI({
     features: [useStdio()],
 });
 ```
+
+## Implementation Status
+
+| `API` | `Status` | `Notes` |
+|-------|----------|---------|
+| `args_XXX` | ✅ | |
+| `clock_XXX` | ✅ | Monotonic clock is unavailable due to JS API limitation |
+| `environ_XXX` | ✅ | |
+| `fd_XXX` | 🚧 | stdin/stdout/stderr are supported |
+| `path_XXX` | ❌ | |
+| `poll_oneoff` | ❌ | |
+| `proc_XXX` | ✅ | |
+| `random_get` | ✅ | |
+| `sched_yield` | ❌ | |
+| `sock_XXX` | ❌ | |