Update README.md

Hzxin · web-flow · commit d15c51f4fbf1 · 2021-02-15T03:14:34.000-08:00
diff --git a/docs/README.md b/docs/README.md
@@ -1,6 +1,6 @@
 # Duke User Guide 
 
-<p align="centre">
+<p align="center">
     <img src="./Ui.png" width="400" heigh = "600">
 </p>
 
