Feature Request: Number of unread chapters while reading manga

Please add the number of unread chapters to the page informations. 

![image](https://user-images.githubusercontent.com/657768/136183171-f7e4e2b4-57e4-4a1b-83c9-0ae3413929b3.png)

![image](https://user-images.githubusercontent.com/657768/136183195-161b61df-0eb1-4903-8d88-53a66387e37c.png)