feat: add Telegram Desktop package

Repackages the official static tsetup.7.0.5.tar.xz Linux build for
amd64, keeping the upstream org.telegram.desktop desktop-id and
TelegramDesktop WM class.

telegram-desktop/org.telegram.desktop.desktop

@@ -0,0 +1,22 @@
+[Desktop Entry]
+Name=Telegram
+Comment=New era of messaging
+TryExec=telegram-desktop
+Exec=telegram-desktop -- %U
+Icon=org.telegram.desktop
+Terminal=false
+StartupWMClass=TelegramDesktop
+Type=Application
+Categories=Chat;Network;InstantMessaging;Qt;
+MimeType=x-scheme-handler/tg;x-scheme-handler/tonsite;
+Keywords=tg;chat;im;messaging;messenger;sms;tdesktop;
+Actions=quit;
+DBusActivatable=false
+SingleMainWindow=true
+X-GNOME-UsesNotifications=true
+X-GNOME-SingleWindow=true
+
+[Desktop Action quit]
+Exec=telegram-desktop -quit
+Name=Quit Telegram
+Icon=application-exit