add a restore initial code button

[simitsu]

🚀 Feature Proposal

A clear and concise description of what the feature is.

Motivation

Please outline the motivation for the proposal.

Contribution

Please describe the solution if you'd like to submit a PR.

[theashggl]

Your code is either saved on Leetcode if you submit it or your local text file where you edit it. So it seems this feature is already there.