Make "Preview" button a dropdown button for multi-store support

[Charlie-Brownie]

We recently changed our Product/Topic/Blog/etc pages so that the Preview button supports multi-store, using the same dropdown button as the Export button. Being able to select from one of the many stores is super handy for us.

See PR - #7363

P.S. This selection dropdownlist should be displayed only when you have several stores configured.

[AndreiMaz]

@Charlie-Brownie Sure, please make a PR

[Charlie-Brownie]

I looked at putting the Favicon into the drop down list but discovered that it only works in my company's solution because all of our stores have the same <link> format. I abandoned this idea since the Favicons aren't setup to be used in the manner I was trying to use them in 👍

[AndreiMaz]

See PR - #7363

[AndreiMaz]

@Charlie-Brownie Thanks a lot! We'll check it

[Charlie-Brownie]

P.S. This selection dropdownlist should be displayed only when you have several stores configured.

Updated my PR to reflect this requirement 👍
Makes sense since non-multistore configurations would have to do an extra unnecessary step