Package Gnome Extension together with snap app

[KenT]

Hi all,

After I left previous comment, I find Snap does not support Gnome-shell extensions now.

Yaru dark theme toggle review request

@pedronis and I discussed this in Vancouver and came to the conclusion to uphold that gnome-shell extensions are not candidates for classic since while snapd could be made to put the extension in the correct location, there are no guarantees the extension shipped in the snap would work with the install gnome-shell. Furthermore, gnome-shell itself would need to be rearchitected to support launching extensions under a different security context otherwise the snap would run outside of confinement.