Split up `check_signals_update`?

[caldwellst]

Do we possibly want to split up the code in src/alerts/check_signals_update.R? It has functions to check for updates, and then also does the runs. The rest of the code in src/alerts (and src/utils, src/images, src/email) are all utilities modules but don't actually do any runs. The only run scripts are in src/indicators. So maybe we actually split off src/indicators and something else for checking the updates that puts them in a runs/ folder or something to that effect?

Might be useful if we also build out more functionality to do "approvals" or other parts of the triage process through GitHub, where we would want an R script to run.

[caldwellst]

I would like to split these up, now that working a bit on the Slack script. Should we change the directory structure to keep src:

1. move src/indicators to runs/indicators
2. create a runs/other or something where the Slack runs go
3. rename src-static to runs-static

Thoughts @zackarno @hannahker?