Feature: add optional Wayland support

Currently, if I want to run VSCode in native Wayland mode, I need to either (1) launch from the terminal and pass ozone flags or (2) modify the desktop file and add those flags. Neither method is particularly good.

I propose that this this VSCode flatpak should [follow in the steps of the Discord flatpak](https://github.com/flathub/com.discordapp.Discord/commit/a2f7a449af1af18a36e2547a2658cf5be5e986d5) and add an optional native Wayland mode. With the Discord flatpak, it by default only comes with X11 access. But if you grant it Wayland access, it will automatically launch in native Wayland mode.