docs: update slogan

Author: gusye1234

README.md

@@ -3,7 +3,7 @@
       <img alt="Show Acontext header banner" src="./assets/Acontext-header-banner.png">
   </a>
   <p>
-    <h3>Scale for your Agents, Improve for your Users</h3>
+    <h3>Scale for the Context, Learn for the Agent</h3>
   </p>
   <p align="center">
     <a href="https://pypi.org/project/acontext/"><img src="https://img.shields.io/pypi/v/acontext.svg"></a>
@@ -32,6 +32,7 @@
 
 
 
+
 Acontext is a context data platform that:
 
 - **Stores** contexts & artifacts