Setup dev and prod deploys on CD

[maurolepore]

Deploy to prod only after coping the home page and ensuring it works fine

.github/workflows/shiny-deploy.yaml now deploys first to staging, then on success to production:

• https://mauro-2dii.shinyapps.io/tiltwebtool-staging/
• https://mauro-2dii.shinyapps.io/tiltwebtool/