I achieved this effect by using this custom css.
.--theme-style-[YOUR TILE THEME NAME] .icon {
-webkit-filter: drop-shadow(0 0 3px #ff0)drop-shadow(0 0 10px #ff0);
filter: drop-shadow(0 0 3px yellow)drop-shadow(0 0 10px yellow);}
This is a supertile with that effect.