doc: update list of people in SECURITY.md

Update the list of people with access to:
- Private security reports against Node.js.
- Private security patches to Node.js.

The latter by running `ncu-team sync SECURITY.md`.

Signed-off-by: Richard Lau <richard.lau@ibm.com>
PR-URL: https://github.com/nodejs/node/pull/64152
Refs: https://github.com/nodejs/Release/issues/733
Refs: https://github.com/nodejs/TSC/issues/1760
Reviewed-By: Beth Griggs <bethanyngriggs@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>

SECURITY.md

@@ -550,6 +550,7 @@ In addition, these individuals have access:
 * [cjihrig](https://github.com/cjihrig) **Colin Ihrig**
 * [joesepi](https://github.com/joesepi) - **Joe Sepi**
 * [juanarbol](https://github.com/juanarbol) **Juan Jose Arboleda**
+* [sxa](https://github.com/sxa) - **Stewart X Addison**
 * [ulisesgascon](https://github.com/ulisesgascon) **Ulises Gascón**
 * [vdeturckheim](https://github.com/vdeturckheim) - **Vladimir de Turckheim**
 
@@ -564,6 +565,7 @@ the Node.js program on HackerOne.
 * [@anonrig](https://github.com/anonrig) - Yagiz Nizipli
 * [@bengl](https://github.com/bengl) - Bryan English
 * [@benjamingr](https://github.com/benjamingr) - Benjamin Gruenbaum
+* [@BethGriggs](https://github.com/BethGriggs) - Beth Griggs
 * [@bmeck](https://github.com/bmeck) - Bradley Farias
 * [@bnoordhuis](https://github.com/bnoordhuis) - Ben Noordhuis
 * [@BridgeAR](https://github.com/BridgeAR) - Ruben Bridgewater
@@ -586,6 +588,7 @@ the Node.js program on HackerOne.
 * [@ruyadorno](https://github.com/ruyadorno) - Ruy Adorno
 * [@santigimeno](https://github.com/santigimeno) - Santiago Gimeno
 * [@ShogunPanda](https://github.com/ShogunPanda) - Paolo Insogna
+* [@sxa](https://github.com/sxa) - Stewart X Addison
 * [@targos](https://github.com/targos) - Michaël Zasso
 * [@tniessen](https://github.com/tniessen) - Tobias Nießen
 * [@UlisesGascon](https://github.com/UlisesGascon) - Ulises Gascón