Cache supported image types

[Maingron]

Once the site has loaded and the images have been spawned by this script, it is not necessary to check for supported image types again for at least the time of the current session.
A setting should be added that allows to cache supported image types as either Cookies, maybe in localstorage and no caching.
Would probably result in something like $_COOKIES['SupportedImageTypes'] = {'png','jpg',...}