chore(core): Export order merge strategies

Relates to #669

packages/core/src/config/index.ts

@@ -21,8 +21,13 @@ export * from './logger/noop-logger';
 export * from './logger/vendure-logger';
 export * from './merge-config';
 export * from './order/custom-order-process';
+export * from './order/default-stock-allocation-strategy';
+export * from './order/merge-orders-strategy';
 export * from './order/order-code-strategy';
 export * from './order/order-merge-strategy';
+export * from './order/use-existing-strategy';
+export * from './order/use-guest-strategy';
+export * from './order/use-guest-if-existing-empty-strategy';
 export * from './order/order-item-price-calculation-strategy';
 export * from './order/stock-allocation-strategy';
 export * from './payment-method/dummy-payment-method-handler';