chore: add Stuart Pearson as maintainer (github-aws-runners#4982)

This PR starts the process of Stuart getting involved with maintaining
this Repo.

---------

Co-authored-by: Niek Palm <npalm@users.noreply.github.com>

Author: 2 people

MAINTAINERS.md

@@ -11,6 +11,7 @@ Roles and responsibilities of the maintainers of the project.
 | Guilherme Caulada | [@guicaulada]       | Grafana Labs     |
 | Ederson Brilhante | [@edersonbrilhante] | Cisco            |
 | Brend Smits       | [@Brend-Smits]      | Philips          |
+| Stuart Pearson    | [@stuartp44]        | Philips          |
 
 ## Responsibilities