feat: integrate demo GIF into README for visual appeal

Integrates the `learnloop_demo.gif` into the "Project Overview" section of the README.md to visually showcase the product's value proposition and core loop to potential contributors and partners.

docs: refactor README.md for clarity

* Remove redundant introductory text that duplicates the repository's "About" description.
* Change the heading from "About the Project" to "Project Overview" to improve structure and avoid repetition.
* Bold the author's name in the Team section to improve visual hierarchy.