Added new approach to 0001-two-sum.md

[DeepC004]

Change Summary

Added a new approach to solve the 0001-two-sum.md problem.

Checklist

Ideally all of them should be checked. If you haven't fulfilled the below requirements or even delete the entire checklist, your PR won't be reviewed.

General

• [x] Make sure you've read CONTRIBUTING.md
• [x] Make sure you've followed the template format
• [x] Make sure you've started the app locally and verified all the content and all links (if applicable) must be accessible correctly
• [x] Make sure you've applied LaTex for variables, formulas and time / space complexity instead of using backticks
• [x] Make sure you've formatted your code well (Code Block is rendered using <Tabs/>) Below is a C++ example. You can include multiple langs using <TabItem/> if necessary

<Tabs>

<TabItem value="cpp" label="C++">
<SolutionAuthor name="@YOUR_ALIAS"/>

```cpp
// Your code goes here
// Prefer K&R Coding style
// See https://gist.github.com/jesseschalken/0f47a2b5a738ced9c845#why-kr for example
```

</TabItem>

</Tabs>

• [x] Make sure you've explained your code well (write comments above each line - not inline)
• [x] Make sure you've written your explanation well and it is easy to understand for beginners
• [x] Make sure you've included Time & Space Complexity Analysis
• [x] Make sure you've included a meaningful approach name for your solution. Don't leave it blank. e.g. ## Approach 1: Two Pointers.

For Tutorial Articles

• [ ] Make sure you've explained your topic using 1 - 3 LC problems rather than using external problems. Solutions must be taken with explanations as well.
• [ ] Make sure you've provided suggested problems at the end using the given format. See here as an example. If the target solution is not available, leave solutionLink blank.
• [ ] Make sure you've given credits / references if you use external resources. For an image, give credit under it. Otherwise, add a new section called References at the end (after Suggested Problems).

[DeepC004]

I have made the changes and tested locally. Code runs fine. Attaching a picture for reference