Better documentation for router getScreenOptions

The documentation of getScreenOptions needs some clarification:

• the headline is getScreenOptions(navigation, screenProps) but the text explains 3 parameters. What is about navigationOptions?
• The text says "retrieve the navigation options for a screen". Why the function is named screen options while it returns navigation options?
• The example code uses addNavigationHelpers which does not exits anymore?
• For me is not clear where I can use this function, p.ex. in screen, in my custom router, etc. Please improve the example to make this more clear.

從連結的 custom-routers 文件中的 getScreenOptions 區段開始，檢視其簽章、說明以及使用 addNavigationHelpers 的範例。釐清參數、術語、目前 API 的用法，以及該函式的使用位置；當範例和周圍文字能回答每一點，且不依賴過時的 API 時，即表示完成。