[feature request] Provide an option to hide the icon on status bar

[yttriumz]

Maybe we can introduce a new setting option z-reader.showInStatusBar with the following behaviors:

• "always": always show in status bar, like the current behavior
• "whenReading": only show when a book is being read
• "never": do not show in status bar

[dr110297]

加个状态栏显示阅读确实不错