Launching a web site as a boarderless window in Google Chrome broswer can be done using 'More Tools -> Create Shortcut'. This works and gives an icon even but i have seen them break or go away. Sometimes they will launch in a boarderless window and sometimes not.
Use the --app option when launching google-chrome command.
google-chrome --app=https://mail.google.gom
Of course, creating a launcher in a desktop would be preferred. Icons for desktops will need to be downloaded separately.