update README

Rich-Harris · Rich-Harris · commit 093543c40273 · 2022-08-26T12:34:54.000-04:00
diff --git a/README.md b/README.md
@@ -8,6 +8,7 @@ Like `JSON.stringify`, but handles
 - regular expressions
 - dates
 - `Map` and `Set`
+- `BigInt`
 
 Try it out on [runkit.com](https://npm.runkit.com/devalue).
 
