Use html to report value diff

The design should like this:

![image](https://user-images.githubusercontent.com/1415488/115971745-30a0a580-a585-11eb-8d29-8c782ba5db77.png)

![image](https://user-images.githubusercontent.com/1415488/115971787-6c3b6f80-a585-11eb-9a2a-a4bc352747ea.png)
