DEVELOPERS: add Christian Stewart to balena-engine package

Signed-off-by: Christian Stewart <christian@paral.in>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

DEVELOPERS

@@ -538,6 +538,7 @@ N:	Christian Kellermann <christian.kellermann@solectrix.de>
 F:	package/python-pylibftdi/
 
 N:	Christian Stewart <christian@paral.in>
+F:	package/balena-engine/
 F:	package/batman-adv/
 F:	package/catatonit/
 F:	package/cni-plugins/