message: Fix default fullscreen binding docs
diff: @@ -517,6 +517,7 @@ key_bindings:
  #- { key: Add, mods: Control, action: IncreaseFontSize }
  #- { key: Subtract, mods: Control, action: DecreaseFontSize }
  #- { key: Minus, mods: Control, action: DecreaseFontSize }
  + #- { key: Return, mods: Alt, action: ToggleFullscreen }
  # (macOS only)
  #- { key: Key0, mods: Command, action: ResetFontSize }
  @@ -530,6 +531,7 @@ key_bindings:
  #- { key: H, mods: Command, action: Hide }
  #- { key: Q, mods: Command, action: Quit }
  #- { key: W, mods: Command, action: Quit }
  + #- { key: F, mods: Command|Control, action: ToggleFullscreen }
  - { key: Paste, action: Paste }
  - { key: Copy, action: Copy }
  