docs: add Launch-on-REANA badges

Note: similar to and depends on https://github.com/reanahub/reana-demo-helloworld/issues/60

Add "Launch-on-REANA" badges to the README file.

We have a lot of reana-*.yaml, so think about a nice presentation.

We can restrict ourselves to only four badges, cwl/serial/snakemake/yadage.

We don't have to cover HTCondor or Slurm.