Add spot lights

[Spotlights](https://docs.microsoft.com/en-us/windows/win32/direct3d9/light-types#spotlight) have a direction, a position, and a cone in which they are bright, defined by an angle Θ, and an outer cone in which they still shed some light, defined by an angle ɸ, with the light intensity diminishing from Θ to ɸ.