docs: update version (#751)

README.md

@@ -31,7 +31,7 @@ yarn add signature_pad
 You can also add it directly to your page using `<script>` tag:
 
 ```html
-<script src="https://cdn.jsdelivr.net/npm/signature_pad@4.0.0/dist/signature_pad.umd.min.js"></script>
+<script src="https://cdn.jsdelivr.net/npm/signature_pad@4.1.7/dist/signature_pad.umd.min.js"></script>
 ```
 
 You can select a different version at [https://www.jsdelivr.com/package/npm/signature_pad](https://www.jsdelivr.com/package/npm/signature_pad).