chore: add MermaidChart to sponsors in README (#1513)

Author: ymc9

README.md

@@ -234,6 +234,7 @@ Thank you for your support!
 
 <table>
   <tr>
+   <td align="center"><a href="https://github.com/Mermaid-Chart"><img src="https://avatars.githubusercontent.com/u/117662492?s=200&v=4" width="100" style="border-radius:50%" alt="Mermaid Chart"/><br />Mermaid Chart</a></td>
    <td align="center"><a href="https://github.com/coderabbitai"><img src="https://avatars.githubusercontent.com/u/132028505?v=4" width="100" style="border-radius:50%" alt="CodeRabbit"/><br />CodeRabbit</a></td>
    <td align="center"><a href="https://github.com/j0hannr"><img src="https://avatars.githubusercontent.com/u/52762073?v=4" width="100" style="border-radius:50%" alt="Johann Rohn"/><br />Johann Rohn</a></td>