Add default exports for Volume and Network modules

Signed-off-by: Cameron Diver <cameron@balena.io>

src/compose/network.ts

@@ -235,3 +235,5 @@ export class Network {
 		return `${appId}_${name}`;
 	}
 }
+
+export default Network;

src/compose/service.ts

@@ -1027,3 +1027,5 @@ export class Service {
 		];
 	}
 }
+
+export default Service;