Hi,
It is not a problem of HikaShop.
HikaShop loads and stores the data in UTF8. So it supports all the characters included in UTF8 including emojis.
However, if you want that the stored emoji code is displayed as what you see on that website, it requires that the font used to display that texts supports the emoji code. And that will be hard to find unless you use the same font they use on their website.
As you can see on that website, they load a bunch of fonts for the emojis :
monosnap.com/file/dg1pwdkSWF1OBKz91cKLDMMsixeV0r
So that would mean that you would need to modify your template to add emoji supporting fonts to it, but it also depends on the browser and OS of the user.
For example, here is a thread about emoji issues on Joomla (which isn't really a Joomla issue):
issues.joomla.org/tracker/joomla-cms/9956
I would rather recommend to use images instead of emoji codes. The images will display exactly the same, regardless of the browser, the OS or the fonts on your website.