update readme

Author: EmilHvitfeldt

README.md

@@ -19,6 +19,8 @@ Adding the one of the following classes adds an icon in the file tab. File an is
 
 - `.sass`
 
+The `width` argument can be used directly in the code fence.
+
 ## Example
 
 Here is the source code for a minimal example: [example.qmd](example.qmd).