Update readme.md

readme.md

@@ -30,7 +30,7 @@ Automatically extract snippets from code and injecting them into markdown docume
 ## Behavior
 
  * Recursively scan the target directory for code files containing snippets. (See [exclusion](/docs/exclusion.md)).
- * Recursively scan the target directory for markdown (`.md`) files. (See [Document Scanning](#document-convention)).
+ * Recursively scan the target directory for markdown (`.md` or `mdx`) files. (See [Document Scanning](#document-convention)).
  * Merge the snippets into those markdown files.