testing/electron: improve default flags
do not add flags if ELECTRON_RUN_AS_NODE=1 - with this var electron behaves like node.js and doesn't like unknown flags.
$ ELECTRON_RUN_AS_NODE=1 electron
/usr/lib/electron/electron: bad option: --ozone-platform-hint=auto
there's also a hack for code-oss to still pass the flags as usually.
WaylandWindowDecorations makes the apps usable on gnome wayland. WebRTCPipeWireCapturer allows to screen-share in webrtc calls for more wayland users.