snapcaft.yaml: Set the AppStream ID in the Snap metadata

This allows software store to recognise this snap matches Visual Studio Code in
other formats (.deb, .rpm, Flatpak etc). It also means reviews on ODRS are
grouped together.

resources/linux/snap/snapcraft.yaml

@@ -51,6 +51,7 @@ apps:
   @@NAME@@:
     command: electron-launch $SNAP/usr/share/@@NAME@@/bin/@@NAME@@
     desktop: usr/share/applications/@@NAME@@.desktop
+    common-id: @@NAME@@.desktop
     environment:
       DISABLE_WAYLAND: 1
       GSETTINGS_SCHEMA_DIR: $SNAP/usr/share/glib-2.0/schemas