fix: use id instead of SKU (#39)

Use entity_id in the WHERE clause instead of sku. This adjustment enhances the query's speed, especially when dealing with a large number of products.

During local testing, the export time decreased significantly from 50 minutes to just 8 minutes. Resulting in an increase in speed of 84%. This speed increase only seems to occur if you don't have all numbers as sku's.

README.md

@@ -9,7 +9,6 @@ composer require tweakwise/magento2-tweakwise-export
 
 Enable module
 
-
 If 'Store Level Export' enabled single store feed  can be generated using the command line.
 ```sh
 php bin/magento tweakwise:export --store '<storecode>'