Enhance CONTRIBUTING.md: Shields to capture the attention of potential contributors

[devactivity-team]

I noticed you have opened issues labeled help wanted. I recommend enhancing the CONTRIBUTING to make the call for new contributors more prominent.

Changes Made:

1. Shields: Added Shields.io badges at the top

[![GitHub repo Good Issues for newbies](https://img.shields.io/github/issues/gnolang/gno/good%20first%20issue?style=flat&logo=github&logoColor=green&label=Good%20First%20issues)](https://github.com/gnolang/gno/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22) [![GitHub Help Wanted issues](https://img.shields.io/github/issues/gnolang/gno/help%20wanted?style=flat&logo=github&logoColor=b545d1&label=%22Help%20Wanted%22%20issues)](https://github.com/gnolang/gno/issues?q=is%3Aopen+is%3Aissue+label%3A%22help+wanted%22) [![GitHub Help Wanted PRs](https://img.shields.io/github/issues-pr/gnolang/gno/help%20wanted?style=flat&logo=github&logoColor=b545d1&label=%22Help%20Wanted%22%20PRs)](https://github.com/gnolang/gno/pulls?q=is%3Aopen+is%3Aissue+label%3A%22help+wanted%22) [![GitHub repo Issues](https://img.shields.io/github/issues/gnolang/gno?style=flat&logo=github&logoColor=red&label=Issues)](https://github.com/gnolang/gno/issues?q=is%3Aopen)

Why This Matters:

• Attract New Contributors: Considering there is a number of opened issues labeled 'Help Wanted' - a welcoming and appealing README is one of the most efficient ways to attract new contributors

🚀 Thank you for considering this pull request! 🚀

[devactivity-team]

I also suggest enhancing the README or CONTRIBUTING with the following widgets using devActivity app:

1. Dynamic Top Contributors (with avatars linked to contributor profiles)

2. Repo Stats

Feel free to explore the Live Demo and Public Dashboard for a quick overview of the app.
It makes the contribution process more exciting with gamification elements like:

• 🌟 XP and Levels based on contributions
• 🏆 Challenges and Achievements
• 🏅 Leaderboard and much more!

Latest repositories using devActivity: barecheck (⭐55)

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Simply install an app to bring a more comprehensive and engaging community experience.

🌟 Happy Coding! 🌟

[thehowl]

automated PR with intention to spam author's product.

to others reading, if you think shields would be a good contribution in line with what we're building, make a separate pull request.