MAINTAINERS: Add MG100 board to Laird Connectivity Platforms

Add the MG100 board as a Laird Connectivity platform

Signed-off-by: Ryan Erickson <ryan.erickson@lairdconnect.com>
diff --git a/MAINTAINERS.yml b/MAINTAINERS.yml
index 96d9a72..9902506 100644
--- a/MAINTAINERS.yml
+++ b/MAINTAINERS.yml
@@ -1286,6 +1286,7 @@
     - boards/arm/bt510/
     - boards/arm/bt610/
     - boards/arm/pinnacle_100_dvk/
+    - boards/arm/mg100/
   labels:
     - "platform: Laird Connectivity"