Update readme.txt with 5.3.0 changelog

Author: ralucaStan

readme.txt

@@ -85,6 +85,30 @@ Release and roadmap notes available on the [WooCommerce Developers Blog](https:/
 
 == Changelog ==
 
+= 5.3.0 - 2021-06-07 =
+
+#### Enhancements
+
+- Hide the Cart and Checkout blocks from the new block-based widget editor. ([4303](https://github.com/woocommerce/woocommerce-gutenberg-products-block/pull/4303))
+- Provide block transforms for legacy widgets with a feature-complete block equivalent. ([4292](https://github.com/woocommerce/woocommerce-gutenberg-products-block/pull/4292))
+
+#### Bug Fixes
+
+- Fix some missing translations from the Cart and Checkout blocks. ([4295](https://github.com/woocommerce/woocommerce-gutenberg-products-block/pull/4295))
+- Fix the flickering of the Proceed to Checkout button on quantity update in the Cart Block. ([4293](https://github.com/woocommerce/woocommerce-gutenberg-products-block/pull/4293))
+- Fix a bug in which Cart Widget didn't update when adding items from the All Products block. ([4291](https://github.com/woocommerce/woocommerce-gutenberg-products-block/pull/4291))
+- Fix a display issue when itemized taxes are enabled, but no products in the cart are taxable. ([4284](https://github.com/woocommerce/woocommerce-gutenberg-products-block/pull/4284))
+- Fix an issue where an attempt to add an out-of-stock product to the cart was made when clicking the "Read more" button. ([4265](https://github.com/woocommerce/woocommerce-gutenberg-products-block/pull/4265))
+
+#### Compatibility
+
+- Add the ability for extensions to register callbacks to be executed by Blocks when the cart/extensions endpoint is hit. Extensions can now tell Blocks they need to do some server-side processing which will update the cart. ([4298](https://github.com/woocommerce/woocommerce-gutenberg-products-block/pull/4298))
+
+#### Various
+
+- Add Slot in the Discounts section of the cart sidebar to allow third party extensions to render their own components there. ([4248](https://github.com/woocommerce/woocommerce-gutenberg-products-block/pull/4248))
+- Move `ValidatedTextInput` to the `@woocommerce/blocks-checkout` package. ([4238](https://github.com/woocommerce/woocommerce-gutenberg-products-block/pull/4238))
+
 = 5.2.0 - 2021-05-25 =
 
 #### Enhancements