v6.8.1

Group invite links now open (#186). Clicking a chat.whatsapp.com group
invite (which reaches the app as a whatsapp://chat?code=… link) used to do
nothing. Whatly now opens WhatsApp Web's own "Join group" preview for it, so the
invite can be accepted from the desktop app.

A sound for new-message notifications (#120). Notifications now ask the
desktop's notification service to play its new-message sound, which some setups
stayed silent without. It is on by default and can be turned off under
Notifications with the new "Play sound" option.

Voice and video calls now open in their own Whatly window. WhatsApp Web's
"Move to new window" during a call (the call popout) used to do nothing: the
window request was handed to the browser or discarded, so the popped-out call had
nowhere to live. Whatly now hosts that popout in a proper Whatly window, with the
microphone, camera and screen-share permissions it needs, and closes it when the
call ends. Genuine external links still open in your browser as before. Voice and
video calls themselves work out of the box (#106, #43, #287, #112, #218, #187).

Each account tab shows its WhatsApp Web version. Hovering an account tab now
lists the WhatsApp Web version in use and the page build token, so a mismatch
between accounts is visible at a glance. The tooltip is translated into all
sixteen languages.