Implement SpotLight #21
Description
$ rg -tcpp 'public Light' ~/git/github/pbrt-v3/src
...
/home/jan/git/github/pbrt-v3/src/lights/spot.h
49:class SpotLight : public Light {
...{{ message }}
$ rg -tcpp 'public Light' ~/git/github/pbrt-v3/src
...
/home/jan/git/github/pbrt-v3/src/lights/spot.h
49:class SpotLight : public Light {
...