feat: Add as non-Steam game: Steamify in the Steam library, under the shortcut; controller works when started from Steam

ui/qml/AppState.qml

@@ -81,6 +81,8 @@ Item {
         if (id === "poweroff" && w.poweroff) w.machine = true;
         if (id === "machine" && !w.machine) w.kpin = false;
         if (id === "kpin" && w.kpin) w.machine = true;
+        if (id === "launcher" && items.some(function (i) { return i.id === "steamgame"; })) w.steamgame = w.launcher;
+        if (id === "steamgame" && w.steamgame) w.launcher = true;
         want = w;
     }
     function computePlan() {

ui/qml/Texts.qml

@@ -21,6 +21,9 @@ QtObject {
         launcher: { label: "Steamify shortcut", hint: "The app on the desktop and in the launcher",
                     body: "Opens the newest Steamify app, so you never need the install command again. Steamify Terminal in the launcher opens the terminal menu.",
                     changes: ["Steamify CachyOS on the desktop and in the launcher (the app)", "Steamify Terminal in the launcher"] },
+        steamgame: { label: "Add as non-Steam game", hint: "Steamify in your Steam library",
+                     body: "Adds Steamify to your Steam library as a non-Steam game. Started from Steam it gets your controller (a Steam Controller only talks to Steam while Steam runs), and you can open it in gaming mode. Steam closes for a moment and starts again, since it only reads its games list at startup: so this is done from the desktop, not from gaming mode or with Steamify started from Steam.",
+                     changes: ["Steamify CachyOS in your Steam library, with its icon", "An entry that's already there is updated, not added twice", "Off (or the shortcut off): removed from the library again"] },
         notify: { label: "Update notifications", hint: "A notification when there's a new Steamify",
                   body: "Checks once a day and when you log in to the desktop. When there's a new Steamify you get a notification and a tray icon: open the app to see what's new and choose what to update, or skip that version. It never updates anything by itself.",
                   changes: ["A daily check (systemd user timer), only on the desktop", "Tray icon only while an update is waiting", "Skip this version: quiet until the next one"] },