Update ReadME

Author: qiauil

README.md

@@ -4,7 +4,9 @@
 </h1>
 <h4 align="center">Convolutional Differential Operators for Physics-based Deep Learning Study</h4>
 <h6 align="center">Calculate the spatial derivative differentiablly!</h6>
-
+<p align="center">
+  [<a href="https://qiauil.github.io/ConvDO/">📖 Documentation & Examples</a>]
+</p>
 
 ## Installation