MAINTAINERS: Add Bryan Boreham, Ayoub Mrini (#13771)

Also simplify structure. Ordering of 'general' maintainers is alphabetical by 2nd name.

Signed-off-by: Bryan Boreham <bjboreham@gmail.com>

MAINTAINERS.md

@@ -1,6 +1,10 @@
 # Maintainers
 
-Julien Pivotto (<roidelapluie@prometheus.io> / @roidelapluie) and Levi Harrison (<levi@leviharrison.dev> / @LeviHarrison) are the main/default maintainers, some parts of the codebase have other maintainers:
+General maintainers:
+* Bryan Boreham (bjboreham@gmail.com / @bboreham)
+* Levi Harrison (levi@leviharrison.dev / @LeviHarrison)
+* Ayoub Mrini (ayoubmrini424@gmail.com / @machine424)
+* Julien Pivotto (roidelapluie@prometheus.io / @roidelapluie)
 
 * `cmd`
   * `promtool`: David Leadbeater (<dgl@dgl.cx> / @dgl)
@@ -19,7 +23,6 @@ George Krajcsovits (<gyorgy.krajcsovits@grafana.com> / @krajorama)
     * `module`: Augustin Husson (<husson.augustin@gmail.com> @nexucis)
 * `Makefile` and related build configuration: Simon Pasquier (<pasquier.simon@gmail.com> / @simonpasquier), Ben Kochie (<superq@gmail.com> / @SuperQ)
 
-
 For the sake of brevity, not all subtrees are explicitly listed. Due to the
 size of this repository, the natural changes in focus of maintainers over time,
 and nuances of where particular features live, this list will always be