MAINTAINERS: Add Yongxu Wang as Firmware collaborator

Add myself as a collaborator for the firmware drivers subsystem.
I have been actively contributing to SCMI protocol implementations
and will continue developing new features, reviewing patches,
and testing firmware functionality

Signed-off-by: Yongxu Wang <[email protected]>

Author: yongxu-wang15

MAINTAINERS.yml

@@ -1684,6 +1684,8 @@ Documentation Infrastructure:
   status: maintained
   maintainers:
     - LaurentiuM1234
+  collaborators:
+    - yongxu-wang15
   files:
     - drivers/firmware/
     - include/zephyr/drivers/firmware/