Adds a border glow if the unit has less health than you.
**note**: This will not work on dummies. Test on something not trivial.
Three sets of colors:
* Red = current hp is less than your max -> Full ToD Available
* Yellow = current hp is less than your configured % -> ToD incoming (by default 150% of your max hp, configurable)
* Teal = <15% (for Improved ToD)