Docs : https://developer.wordpress.org/reference/functions/get_page_by_path/
由頁面的 slug (名稱、代稱、路徑 ) 之字串取得，頁面的物件
example :
參考
https://stackoverflow.com/a/29770273
https://gist.github.com/lcdsantos/b25d21a0afb85bd89a41fc48afb6b609
https://developer.wordpress.org/reference/functions/get_page[……]