Written Readme.md file for convert_xml_to_json.py

[Azhad56]

Description

Written Readme.md file for convert_xml_to_json.py

Fixes #(263)

Type of change

• Documentation Update

Checklist:

Please tick all the boxes that are fulfilled by your Pull Request.

• I have named my files and folder, according to this project's guidelines.
• My code follows the style guidelines of this project.
• My Pull Request has a descriptive title. (not a vague title like Update index.md)
• I have commented on my code, particularly in hard-to-understand areas.
• I have created a helpful and easy to understand README.md, according to the given README_TEMPLATE.
• I have included a requirements.txt file (if external libraries are required.)
• My changes do not produce any warnings.
• I have added a working sample/screenshot of the script.