doc (readme): update banner

README.md

@@ -1,8 +1,11 @@
 <div align="center">
-<img src="./docs/images/banner.jpg" width="520px" alt="PDF2ZH">  
-  
+
 English | [简体中文](README_zh-CN.md)
 
+## PDFMathTranslate
+
+<img src="./docs/images/banner.png" width="320px", alt="PDF2ZH">  
+
 <p>
   <!-- PyPI -->
   <a href="https://pypi.org/project/pdf2zh/">

README_zh-CN.md

@@ -1,9 +1,11 @@
 <div align="center">
 
-<img src="./docs/images/banner.jpg" width="520px", alt="PDF2ZH">  
-  
 [English](README.md) | 简体中文
 
+## PDFMathTranslate
+
+<img src="./docs/images/banner.png" width="320px", alt="PDF2ZH">  
+
 <p>
   <!-- PyPI -->
   <a href="https://pypi.org/project/pdf2zh/">