Add dark mode

[Raksha25]

Create a button that will switch between the original theme and the new theme.

[rezaduha]

hi, i would like to work on this issue

[Daksh-404]

Hi, I want to work on this issue!

[Raksha25]

@Daksh-404 @rezaduha you both can work on this.

[Jaagrav]

@Raksha25 Please check out the pull request I have made... #6

I am working on making it mobile responsive, in the mean time you can check out the stuff I have changed, I have added Ace Editor to it so that it looks more like a code and not just text in an textarea, check it out!