Maintainers.txt: Add missing github ids

Maintainers.txt: Add missing github ids

Cc: Andrew Fish <afish@apple.com>
Cc: Leif Lindholm <quic_llindhol@quicinc.com>
Cc: Daniel Schaefer <daniel.schaefer@hpe.com>
Cc: Sean Rhodes <sean@starlabs.systems>
Cc: Debkumar De <debkumar.de@intel.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: Gary Lin <gary.lin@hpe.com>
Cc: Julien Grall <julien@xen.org>
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Daniel Schaefer <daniel.schaefer@hpe.com>
Reviewed-by: Sean Rhodes <sean@starlabs.systems>
Reviewed-by: Debkumar De <debkumar.de@intel.com>
Acked-by: Gary Lin <gary.lin@hpe.com>
Reviewed-by: Andrew Fish <afish@apple.com>