feat(player): add sleep timer

lib/l10n/arb/app_en.arb

@@ -6053,6 +6053,45 @@
   "@nowPlayingDetails": {
     "description": "Menu item and section title for track metadata details"
   },
+  "nowPlayingSleepTimer": "Sleep timer",
+  "@nowPlayingSleepTimer": {
+    "description": "Menu item and sheet title for the playback sleep timer"
+  },
+  "nowPlayingSleepTimerActive": "Ends at {time}",
+  "@nowPlayingSleepTimerActive": {
+    "description": "Active sleep timer deadline shown in the player menu",
+    "placeholders": {
+      "time": {
+        "type": "String"
+      }
+    }
+  },
+  "nowPlayingSleepTimerMinutes": "{minutes, plural, =1{1 minute} other{{minutes} minutes}}",
+  "@nowPlayingSleepTimerMinutes": {
+    "description": "Duration choice for the playback sleep timer",
+    "placeholders": {
+      "minutes": {
+        "type": "int"
+      }
+    }
+  },
+  "nowPlayingSleepTimerOff": "Turn off sleep timer",
+  "@nowPlayingSleepTimerOff": {
+    "description": "Action to cancel the active playback sleep timer"
+  },
+  "nowPlayingSleepTimerSet": "Sleep timer set for {duration}",
+  "@nowPlayingSleepTimerSet": {
+    "description": "Confirmation after setting the playback sleep timer",
+    "placeholders": {
+      "duration": {
+        "type": "String"
+      }
+    }
+  },
+  "nowPlayingSleepTimerCancelled": "Sleep timer turned off",
+  "@nowPlayingSleepTimerCancelled": {
+    "description": "Confirmation after cancelling the playback sleep timer"
+  },
   "nowPlayingOpenInExternalPlayer": "Open in external player",
   "@nowPlayingOpenInExternalPlayer": {
     "description": "Menu item to open the current track in an external player"