[FEATURE] Add popup after adding to cart on mobile

[akrajna]

Describe how this feature will help us improve
User will be sure that his action 'add to cart' was successfully completed

Describe the solution you'd considered
On mobile - add popup window with information 'Size ... was added to your shopping bag' after adding product to the cart as below:

Acceptance criteria

• the popup appears after user adds product to the cart

[pspaczek]

@akrajna can you add Feature issues at Storefront UI?

[patzick]

@akrajna please add issue as Przemek suggested and link it here

[akrajna]

related issue vuestorefront/storefront-ui#1196