fixup: update the doc

Signed-off-by: Daeyeon Jeong [email protected]

Author: daeyeon

doc/api/process.md

@@ -1716,7 +1716,8 @@ that started the Node.js process. Symbolic links, if any, are resolved.
 added: v0.1.13
 -->
 
-* `code` {integer} The exit code. **Default:** `0`.
+* `code` {integer|string|null|undefined} The exit code. For string type, only
+integer strings (e.g.,'1') are allowed. **Default:** `0`.
 
 The `process.exit()` method instructs Node.js to terminate the process
 synchronously with an exit status of `code`. If `code` is omitted, exit uses