Add Andrey as maintainer
Add Andrey as maintainer

Signed-off-by: Julien Pivotto <df1ed88a312a603dfee9f157a90fa8f7f195ab59@inuits.eu>

GoogleCloudPlatform/alertmanager,GoogleCloudPlatform/alertmanager,prometheus/alertmanager,prometheus/alertmanager,GoogleCloudPlatform/alertmanager,GoogleCloudPlatform/alertmanager,prometheus/alertmanager,prometheus/alertmanager