Add release testing notes

Author: opr

docs/internal-developers/testing/releases/881.md

@@ -0,0 +1,17 @@
+# Testing notes and ZIP for release 8.8.1
+
+Zip file for testing: [woocommerce-gutenberg-products-block.zip](https://github.com/woocommerce/woocommerce-blocks/files/9880626/woocommerce-gutenberg-products-block.zip)
+
+
+## Feature plugin and package inclusion in WooCommerce
+
+### Calculate cart totals after running extensions ([#7490](https://github.com/woocommerce/woocommerce-blocks/pull/7490))
+
+1. Install [WooCommerce Gift Cards](https://woocommerce.com/products/gift-cards/).
+2. Create [a new gift card](https://woocommerce.com/document/gift-cards/store-owners-guide/#creating-gift-card-products) Simple Product and buy it. 
+3. Mark the order as 'Completed'.
+4. Navigate to **Marketing > Gift Cards** and copy the generated gift card code. 
+5. Add a non-gift card product to the cart. 
+6. Navigate to the cart block. 
+7. Apply the gift card you previously copied. You should see: 1) an indication that the gift card was applied, 2) a bullet bubble with the gift card number in this format `XXXX-XXX-XXX-XXX` and 3) updated cart totals that include the gift card discount. 
+8. Remove the gift card. You should see that the cart totals are restored. 

docs/internal-developers/testing/releases/README.md

@@ -97,6 +97,7 @@ Every release includes specific testing instructions for new features and bug fi
     -   [8.7.3](./873.md)
     -   [8.7.4](./874.md)
 -   [8.8.0](./880.md)
+    -   [8.8.1](./881.md)
 
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