binding [nfc]: Expand toggleWakelock doc to clarify what it does

This method's name is based on the library it wraps, which is good.
But that library's name is misleading.  So add more details to the
doc than we usually do for these binding methods, to clear that up.

lib/model/binding.dart

@@ -176,9 +176,17 @@ abstract class ZulipBinding {
     bool requestFullMetadata,
   });
 
-  /// Enables or disables screen wakelock, via package:wakelock_plus.
+  /// Enables or disables keeping the screen on, via package:wakelock_plus.
   ///
   /// This wraps [wakelock_plus.WakelockPlus.toggle].
+  ///
+  /// Despite the name, this does not involve Android's "wake locks".
+  /// The implementation sets FLAG_KEEP_SCREEN_ON on Android:
+  ///   https://developer.android.com/develop/background-work/background-tasks/awake/screen-on
+  ///   https://github.com/fluttercommunity/wakelock_plus/blob/5ca5243e7894830ce289fc367bc5fdec27c7f0cf/wakelock_plus/android/src/main/kotlin/dev/fluttercommunity/plus/wakelock/Wakelock.kt
+  /// and idleTimerDisabled on iOS:
+  ///   https://developer.apple.com/documentation/uikit/uiapplication/1623070-idletimerdisabled
+  ///   https://github.com/fluttercommunity/wakelock_plus/blob/5ca5243e7894830ce289fc367bc5fdec27c7f0cf/wakelock_plus/ios/Classes/WakelockPlusPlugin.m
   Future<void> toggleWakelock({required bool enable});
 }