UI update: open and close eye icon instead of checkboxes

[loveshdongre]

The current implementation uses check boxes however, open and close eye icon conveys the function slightly better

[saptarshithe42]

This pull request is regarding issue https://github.com/loveshdongre/leetcode-enhancer/issues/10 Please review it

[natzelo]

I think we can close this issue now @loveshdongre ?