Time Zone conversion tool

# Create a Time Zone conversion tool in html,css and javascript.

- Add navbar in your tool's html file. You can copy the navbar from index.html.
- Add screenshot of your tool in, PR message and also in the folder of your tool
- Before Making the PR Pull the latest changes that have been made to the repository

**Note: Please Don't Make Any Changes In `index.html` AND `contributors.html` **
--

## Add this to your pr message

## Title

## Number of files/folder added

## changes made

## I have;

- [ ] Read contibuting.md
- [ ] Followed all the guidelines
- [ ] updated readme.md

首先阅读 index.html 了解导航栏，并阅读 contributing.md 了解仓库指南。在不更改 index.html 或 contributors.html 的情况下，添加时区转换工具，将截图放入工具文件夹和 PR 中，并按要求更新 readme.md。

由索引模型根据 Issue 内容生成。