Fix: allow svg in storefront messages, such as notices

[dinhtungdu]

Fixes #2129

This PR fix the missing icon issue of Woo notices with Storefront theme by adding svg and its child elements to the allowed html list for wp_kses().

Alternative

Do nothing, as commented here: #2129 (comment)

Screenshots

How to test the changes in this Pull Request:

1. Create a test page and add the following shortcode to it [woocommerce_cart]
2. Go to a product page and click the Add to cart button.
3. See that the notice “{PRODUCT}” has been added to your cart. shows an icon. ✅
4. Go to the test page from step 1. and update the quantity of the added product.
5. See that the notice Cart updated. shows an icon. ✅
6. Add a coupon code to the cart.
7. See that the notice Coupon code applied successfully. shows an icon. ✅
8. Add the same code again.
9. See that the notice Coupon code already applied! shows an icon. ✅
10. Add an invalid code.
11. See that the notice Coupon "{CODE}" does not exist! shows an icon. ✅
12. Remove the coupon code.
13. See that the notice Coupon has been removed. shows an icon. ✅
14. Remove the product from the cart.
15. See that the notice Your cart is currently empty. shows an icon. ✅
16. See that the notice “{PRODUCT}” removed. Undo? shows an icon. ✅

Changelog

Fix – Allow SVG in Storefront messages. #1319

[albarin]

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