just normal rendering, there is nothing different between 2.79 or 2.8 in how it is done, set a camera, set the resolution for the camera (output properties > dimensions where also the export panel is, set it to 2x the res of the icon and the % to 50)
set the background to transparency (render properties > film)
and then choose wich part should be visible in the render and witch parts not
select the camera and press ctrl+numpad 0 to get into camera view and make your adjustments to fit the image (object data properties > lens, and g +x/y/z for movement)
if you have it press F12 and blender will render it
if you have it shift+s and then save it as a tga with alpha
this should give you an icon in 256x64 with transparent background to use as a shop icon ingame