Add GitHub Action to deploy Shiny app to shinyapps.io

[Copilot]

Summary

Adds .github/workflows/deploy-shiny.yml — a GitHub Actions workflow that automatically deploys the Shiny app in robvisapp/ to shinyapps.io whenever changes to that folder are pushed to the main or master branch.

---

Required Repository Secrets

Before the workflow will work, three secrets must be added to the repository under Settings → Secrets and variables → Actions:

Secret name	Where to find it
SHINYAPPS_ACCOUNT	Your shinyapps.io account name (the subdomain in https://<account>.shinyapps.io)
SHINYAPPS_TOKEN	shinyapps.io dashboard → Account → Tokens → Show → Token value
SHINYAPPS_SECRET	shinyapps.io dashboard → Account → Tokens → Show → Secret value

Step-by-step: getting the token and secret

1. Log in to shinyapps.io.
2. Click your username in the top-right → Account.
3. Go to the Tokens tab.
4. Click + Add Token (or use an existing token).
5. Click Show next to the token — this reveals both the Token and the Secret.
6. Copy each value into the corresponding GitHub secret listed above.

---

What the workflow does

1. Triggers on pushes to main / master that touch files under robvisapp/.
2. Sets up R with the public RStudio Package Manager for fast binary installs.
3. Installs required system libraries and all R package dependencies (including robvis itself from the local source).
4. Authenticates with shinyapps.io using rsconnect::setAccountInfo() and the three secrets above.
5. Deploys the app with rsconnect::deployApp(appDir = "robvisapp", appName = "robvis").