StartupWMClass missing from .desktop file

[MariusQuabeck]

Hey,

please consider adding 

StartupWMClass=spotify

to the .desktop file for the spotify snap. This will make it possible for users to pin spotify to their launchers. 

The .desktop file should look something like this

[Desktop Entry]
Name=Spotify
GenericName=Music Player
Comment=Spotify streaming music client
Icon=${SNAP}/usr/share/spotify/icons/spotify-linux-128.png
Exec=spotify %U
TryExec=spotify
Terminal=false
StartupWMClass=spotify
Type=Application
Categories=Audio;Music;Player;AudioVideo;
MimeType=x-scheme-handler/spotify;

and is located in 

/var/lib/snapd/desktop/applications/spotify_spotify.desktop

this will also solve the issue of multiple Spotify icons appearing in most bars/docks/launchers.

Cheers

Marius