doc: add santigimeno to collaborators

PR-URL: #6225
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Myles Borins <myles.borins@gmail.com>

Author: santigimeno

README.md

@@ -197,6 +197,7 @@ information about the governance of the Node.js project, see
 * [romankl](https://github.com/romankl) - **Roman Klauke** <romaaan.git@gmail.com>
 * [saghul](https://github.com/saghul) - **Saúl Ibarra Corretgé** <saghul@gmail.com>
 * [sam-github](https://github.com/sam-github) - **Sam Roberts** <vieuxtech@gmail.com>
+* [santigimeno](https://github.com/santigimeno) - **Santiago Gimeno** <santiago.gimeno@gmail.com>
 * [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>