Automation of updating submodule and jsons

[tryggvigy]

Hey,

I noticed commits like 3bbd342. I think we can automate keeping covid19_scenarios_data up to date using a github workflow. I created a draft PR to demonstrate #267. What are your thoughts? Curious to hear if you think this could be useful @rneher. We could do the same in the covid19_scenarios_data repository for any periodic tasks.

[nnoll]

I think we solved this by simply integrating the data submodule into this repo. It should reduce this friction completely.