[docs update]知识星球封面更新

Author: Snailclimb

README.md

@@ -26,7 +26,7 @@
   <img src="https://img.shields.io/github/forks/Snailclimb/JavaGuide" alt="forks"/>
   <img src="https://img.shields.io/github/issues/Snailclimb/JavaGuide" alt="issues"/>
 </p>
-<h3 align="center">Sponsor</h3>
+<h3 align="center">推荐</h3>
 <table>
   <tbody>
     <tr>
@@ -38,6 +38,7 @@
   </tbody>
 </table>
 
+
 ## Java
 
 ### 基础