Provide --version Option in Command-Line

[erichlf]

I wanted to provide a version number for a bug, but was unable to get it via command-line interface.

$ whatsapp-for-linux --help-all                                                         
Gtk-Message: 08:50:49.003: Not loading module "atk-bridge": The functionality is provided by GTK natively. Please try to not load it.
Usage:
  whatsapp-for-linux [OPTION…]

Help Options:
  -h, --help                 Show help options
  --help-all                 Show all help options
  --help-gapplication        Show GApplication options
  --help-gtk                 Show GTK+ Options

GApplication options
  --gapplication-service     Enter GApplication service mode (use from D-Bus service files)

GTK+ Options
  --class=CLASS              Program class as used by the window manager
  --name=NAME                Program name as used by the window manager
  --gdk-debug=FLAGS          GDK debugging flags to set
  --gdk-no-debug=FLAGS       GDK debugging flags to unset
  --gtk-module=MODULES       Load additional GTK+ modules
  --g-fatal-warnings         Make all warnings fatal
  --gtk-debug=FLAGS          GTK+ debugging flags to set
  --gtk-no-debug=FLAGS       GTK+ debugging flags to unset

Application Options:
  --display=DISPLAY          X display to use

Seems like a small oversight that could easily be added. The version I am using is apparently 1.6.4 based on the "about" selection from the tray-icon, but I could see a case where whatsapp is crashing and one is unable to get to that menu item; providing a command line option would help with such situations.