Meta: Add Jelle Raaijmakers to list of project maintainers :^)

CONTRIBUTING.md

@@ -82,7 +82,7 @@ Ping them right away if it's something urgent! If it's less urgent, advertise yo
 
 ### Who are the project maintainers?
 
-The project maintainers at this time are [@awesomekling](https://github.com/awesomekling), [@linusg](https://github.com/linusg), [@alimpfard](https://github.com/alimpfard), [@gunnarbeutner](https://github.com/gunnarbeutner), [@bgianfo](https://github.com/bgianfo), [@IdanHo](https://github.com/IdanHo), [@trflynn89](https://github.com/trflynn89), [@AtkinsSJ](https://github.com/AtkinsSJ), and [@ADKaster](https://github.com/ADKaster).
+The project maintainers at this time are [@awesomekling](https://github.com/awesomekling), [@linusg](https://github.com/linusg), [@alimpfard](https://github.com/alimpfard), [@gunnarbeutner](https://github.com/gunnarbeutner), [@bgianfo](https://github.com/bgianfo), [@IdanHo](https://github.com/IdanHo), [@trflynn89](https://github.com/trflynn89), [@AtkinsSJ](https://github.com/AtkinsSJ), [@ADKaster](https://github.com/ADKaster), and [@GMTA](https://github.com/gmta).
 
 Maintainership is by invitation only and does not correlate with any particular metric.