[FR] Inform that the whole package should be uploaded to the server as a comment in app.R when running golem::add_shinyserver_file()

[ColinFay]

When running golem::add_shinyserver_file(), the console output is:

> golem::add_shinyserver_file() 
── Creating _disable_autoload.R ──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────
✔ Created
✔ Adding '^app\\.R$' to '.Rbuildignore'
✔ Adding '^rsconnect$' to '.Rbuildignore'
✔ Adding 'pkgload' to Imports field in DESCRIPTION
• Refer to functions with `pkgload::fun()`
✔ File created at /private/tmp/deleteme/app.R
To deploy, run:
• rsconnect::deployApp()

• Note that you'll need to upload the whole package to Shiny Server

But the app.R doesn't include the Note:

> cat(readLines("app.R"), sep = "\n")
# Launch the ShinyApp (Do not remove this comment)
# To deploy, run: rsconnect::deployApp()
# Or use the blue button on top of this file

pkgload::load_all(export_all = FALSE,helpers = FALSE,attach_testthat = FALSE)
options( "golem.app.prod" = TRUE)
deleteme::run_app() # add parameters here (if any)

Related #1127