Add tab to show the current performance.

[mr-optimizer]

As we are displaying the new rating, old rating and delta, we can show the performance tab also. We can take the reference from Codeforces extensions. (From Current performance I mean, In that particular contest you performed like how much ratings)

We can see the Delta as well as its current performance.

[baoliay2008]

Hi, @mr-optimizer Thanks for your suggestion. I suppose this is something like the expected rating in LeetCode. I will show this in the table.