Update Documentation/GeneralConventions/ReadmeFile.rst

Co-authored-by: Chris Müller <2566282+brotkrueml@users.noreply.github.com>

Documentation/GeneralConventions/ReadmeFile.rst

@@ -91,5 +91,5 @@ The *abstract* placeholder contains a short and precise description of the
 project with as many keywords as possible in as few sentences as possible. It
 helps the decision maker to quickly decide whether the project is worth
 considering and whether or not to read the full documentation. It should be
-aligned with the abstract of Index.rst and - if available - the description
+aligned with the abstract of :file:`Index.rst` and - if available - the description
 fields of :file:`ext_emconf.php` and :file:`composer.json`.