Need a flag to stop web browser opening a new tab after successful deployment to shinyapps.io

[karangattu]

One of the use cases we are trying to solve for CI deployments to shinyapps.io is to not have the default web browser tab being open on every successful deployment due to this line in the code.

If we can have an alternative/flag that allows the user to not have a browser tab being opened after successful deployments. something along the lines of -o, --open_browser [yes|no] If the web browser tab should be automatically opened after deployment yes (default) or no)

so the usage would look like

rsconnect deploy shiny app_file_path --name server_nickname --open_browser no 

[aronatkins]

This is essentially the same as #296. CC @mslynch