doc: add mmarchini to collaborators

PR-URL: #18740
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>

Author: Matheus Marchini

README.md

@@ -426,6 +426,8 @@ For more information about the governance of the Node.js project, see
 **Mikeal Rogers** <mikeal.rogers@gmail.com>
 * [misterdjules](https://github.com/misterdjules) -
 **Julien Gilli** <jgilli@nodejs.org>
+* [mmarchini](https://github.com/mmarchini) -
+**Matheus Marchini**  <matheus@sthima.com>
 * [mscdex](https://github.com/mscdex) -
 **Brian White** <mscdex@mscdex.net>
 * [MylesBorins](https://github.com/MylesBorins) -