Add Counterfact to HTTP Mocking category

[pmcelhaney]

Thank you for contributing to the Node.js Toolbox catalog! 🙏

Note: Node.js Toolbox is specifically for backend libraries. If a library works both in the browser AND in Node.js feel free to add it. Libraries that work ONLY in the browser are out of scope for now.

Before submitting your pull request, please make sure:

• [x] To use the exact package name as it appears on NPM (and npm install <package-name>)
• [x] The packages are listed in alphabetical order
• [x] The package doesn't already exist in a different category
• [x] Description doesn't have a dot (.) at the end
• [x] To format with Prettier before committing (npm run prettier)

More info at https://counterfact.dev

[Maximization]

@pmcelhaney Thanks for your contribution! https://nodejstoolbox.com/categories/http-mocking