[BEAM-13776][Playground] (#16731)
[BEAM-13776][Playground] (#16731)

Update `README.md` for the playground
apache/beam,chamikaramj/beam,chamikaramj/beam,robertwb/incubator-beam,lukecwik/incubator-beam,apache/beam,lukecwik/incubator-beam,lukecwik/incubator-beam,lukecwik/incubator-beam,apache/beam,robertwb/incubator-beam,apache/beam,apache/beam,robertwb/incubator-beam,lukecwik/incubator-beam,lukecwik/incubator-beam,robertwb/incubator-beam,robertwb/incubator-beam,chamikaramj/beam,lukecwik/incubator-beam,chamikaramj/beam,chamikaramj/beam,robertwb/incubator-beam,robertwb/incubator-beam,chamikaramj/beam,robertwb/incubator-beam,apache/beam,chamikaramj/beam,robertwb/incubator-beam,apache/beam,apache/beam,lukecwik/incubator-beam,apache/beam,chamikaramj/beam,robertwb/incubator-beam,lukecwik/incubator-beam,chamikaramj/beam,apache/beam,chamikaramj/beam,lukecwik/incubator-beam,apache/beam