doc: add stefanmb to collaborators

PR-URL: #6227
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Myles Borins <myles.borins@gmail.com>

Author: stefanmb

README.md

@@ -202,6 +202,7 @@ information about the governance of the Node.js project, see
 * [seishun](https://github.com/seishun) - **Nikolai Vavilov** <vvnicholas@gmail.com>
 * [silverwind](https://github.com/silverwind) - **Roman Reiss** <me@silverwind.io>
 * [srl295](https://github.com/srl295) - **Steven R Loomis** <srloomis@us.ibm.com>
+* [stefanmb](https://github.com/stefanmb) - **Stefan Budeanu** <stefan@budeanu.com>
 * [targos](https://github.com/targos) - **Michaël Zasso** <mic.besace@gmail.com>
 * [tellnes](https://github.com/tellnes) - **Christian Tellnes** <christian@tellnes.no>
 * [thealphanerd](https://github.com/thealphanerd) - **Myles Borins** <myles.borins@gmail.com>