Add Story section to README

[Copilot]

This change addresses the request to “create a story” in the README by adding a dedicated narrative section. It introduces a concise project story aligned with the existing Todo App context.

• What does this feature do?

  Adds a new ## Story section to README.md with a short, readable narrative about using testing_mcp and the Todo App.

• Why is this feature needed?

  The issue explicitly asks for story content in the README; this makes that content first-class and easy to find without changing app behavior.

• Implementation details

  The update is documentation-only and appends a new section after the existing usage content.

  ## Story
  
  One rainy afternoon, a developer opened `testing_mcp` to try a small idea.  
  They built a simple Todo App, watched tasks stay saved between refreshes, and smiled when each checkbox click felt effortless.  
  By sunset, the tiny project had become a reliable daily companion for turning scattered thoughts into finished work.