Explain how the root URI is handled

Author: pascal-fb-martin

README.md

@@ -124,3 +124,5 @@ int  echttp_static_route (const char *uri, const char *path);
 Associate a parent URI with a local directory path: a child of the specified URI will match an existing file at the specified path (including the URI's child relative path).
 
 For example if one defines a static route from /static to /home/doe/public, the URI /static/fancy/interface.html will route to /home/doe/public/fancy/interface.html.
+
+As soon as a static route has been declared, the extension takes over the root URI "/". If the root URI is requested, the extension seaches for file index.html in every path provided and returns the content of the first one found.