Fixes: https://github.com/jitsi/jitsi-meet-electron/issues/380

* Fixes #369

Fixes: https://github.com/jitsi/jitsi-meet-electron/issues/371

Update frame-ancestors note.

Fixes a crash when H.264 is used (in P2P mode).

Electron 9 ships with Chrome 83 which means we have access to E2EE by
enabling experimental web platform features.

Don't use abotars, as they are no longer used in Jitsi Meet.

The regular windows shortcuts (eg. minimise, hide) don't work unless
they have menu entries, so add them along with the standard set of
expected menu items for mac (although I've omitted 'about' since it
opens a window so is a slightly more visible change).

Also Electron has a role for 'quit' so use this instead of providing
our own.

- Style
- Layout
- Add spotlight

Ref: https://github.com/jitsi/jitsi-meet-electron/issues/231

This commit will add a toggle to settings drawer to enable/disable the floating (always on top) window during a call (issue #171).
This feature is based on the code from pull request #172 by @gorance-teletrader.

It was not clear that the cask formula was available for this promising app: https://github.com/Homebrew/homebrew-cask/blob/master/Casks/jitsi-meet.rb