Describe the bug

When using http client from dart:io package, the request headers are not shown.

To Reproduce
Steps to reproduce the behavior:

1. Connect Alice to HttpClient from dart:io package according to readme.
2. Send http request with some headers added.
3. Open Alice inspector.
4. Look at the request headers.

Actual behavior
Http headers are not shown for the request.

Expected behavior
Http headers are shown for the request. Also, because of that, Content type is always Unknown.

Alice version
Version: 0.4.2

Additional context
This is an old issue, it was reported and fixed in 2019, but only for HttpClient from http package, and not for the one from dart:io package. See #6 (issue) and #7 (PR) for details.

I created a PR that fixes it.