docs: add note on video/media attrs.

docs/embed-files.md

@@ -73,6 +73,11 @@ Example:
 
 If you embed the file as `iframe`, `audio` and `video`, then you may need to set the attributes of these tags.
 
+?> Note, for the `audio` and `video` types, docsify adds the `controls` attribute by default. When you want add more attributes, the `controls` attribute need to be added manually if need be.  
+```md
+[filename](_media/example.mp4 ':include :type=video controls width=100%')
+```
+
 ```markdown
 [cinwell website](https://cinwell.com ':include :type=iframe width=100% height=400px')
 ```