docs: src of docsify-copy-code (#1585)

Co-authored-by: 沈唁 <[email protected]>

docs/plugins.md

@@ -138,7 +138,7 @@ When readers expand the demo box, the source code and description are shown ther
 Add a simple `Click to copy` button to all preformatted code blocks to effortlessly allow users to copy example code from your docs. Provided by [@jperasmus](https://github.com/jperasmus)
 
 ```html
-<script src="//cdn.jsdelivr.net/npm/docsify-copy-code"></script>
+<script src="//cdn.jsdelivr.net/npm/docsify-copy-code/dist/docsify-copy-code.min.js"></script>
 ```
 
 See [here](https://github.com/jperasmus/docsify-copy-code/blob/master/README.md) for more details.