Fixed small typo in readme

[anderslynge]

Description

Changed tct to txt

Fixes #(issue_no)

no issue

Type of change

Choosing one or more options from the following as per the nature of your Pull request.

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [X] 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.
• [X] 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.)
• [X] My changes do not produce any warnings.
• [ ] I have added a working sample/screenshot of the script.