Add benchmark for js13k-ecs

[rottencandy]

Another tiny ECS library: https://github.com/kutuluk/js13k-ecs
It would be good to have a benchmark for this as well.

I wanted to create a PR for this myself, but I think it's best if all the benchmarks are run from a single device.

[ooflorent]

I've created a PR to add it (#15).

Unfortunately, the library does not run in strict mode (see kutuluk/js13k-ecs#6). The following line raises an error: https://github.com/kutuluk/js13k-ecs/blob/e598de7a43e1703791ded23792738f4769966c6a/src/ecs.js#L186

[kutuluk]

#63