chore: add sponsor badges, BMC funding, and social preview

- FUNDING.yml: add buy_me_a_coffee: ribato
- README: add Buy Me a Coffee ☕ and GitHub Sponsors ❤️ badges
- Social preview image for repo sharing (docs/social-preview.png)

Author: ribato22

.github/FUNDING.yml

@@ -1,6 +1,6 @@
 # These are supported funding model platforms
 
 github: [ribato22]
+buy_me_a_coffee: ribato
 # ko_fi: # Replace with your Ko-fi username
-# buy_me_a_coffee: # Replace with your Buy Me a Coffee username
 # custom: ["https://your-donation-link.com"]

README.md

@@ -15,7 +15,8 @@
   <a href="docker-compose.production.yml"><img src="https://img.shields.io/badge/docker-ready-blue.svg" alt="Docker" /></a>
   <a href="https://github.com/ribato22/multiwa/actions/workflows/ci.yml"><img src="https://github.com/ribato22/multiwa/actions/workflows/ci.yml/badge.svg" alt="CI" /></a>
   <img src="https://img.shields.io/badge/PRs-welcome-brightgreen.svg" alt="PRs Welcome" />
-  <img src="https://img.shields.io/badge/lang-en-blue.svg" alt="English" />
+  <a href="https://buymeacoffee.com/ribato"><img src="https://img.shields.io/badge/Buy%20Me%20a%20Coffee-☕-orange.svg" alt="Buy Me a Coffee" /></a>
+  <a href="https://github.com/sponsors/ribato22"><img src="https://img.shields.io/badge/Sponsor-❤️-ea4aaa.svg" alt="GitHub Sponsors" /></a>
 </p>
 
 <p align="center">