docs: use local logo image in README

- Update README to use assets/figma-vars-tagline.png for the FigmaVars logo
- Ensures reliable image loading and repo portability
- Add logo file to repo for open source best practices

Author: marklearst

README.md

@@ -1,5 +1,9 @@
 # @figma-vars/hooks
 
+<p align="center">
+  <img src="assets/figma-vars-tagline.png" alt="FigmaVars Logo" width="500" />
+</p>
+
 A fast, typed React 19 hooks library for the Figma Variables API: fetch, update, and manage design tokens via the official [Figma REST API](https://www.figma.com/developers/api#variables).
 
 Built for the modern web, this library provides a suite of hooks to fetch, manage, and mutate your design tokens, making it easy to sync them between Figma and your React applications, Storybooks, or design system dashboards.
@@ -197,5 +201,5 @@ PRs and issues are welcome! Please see [CONTRIBUTING.md](CONTRIBUTING.md) for gu
 
 ## 📝 License
 
-This project is licensed under the [MIT License](LICENSE).  
+This project is licensed under the [MIT License](LICENSE).
 © 2024–2025 Mark Learst