Fix some links

Author: alies-dev

library/backend/README.md

@@ -2,10 +2,10 @@
 
 ## Table of Contents
 
--   [IxDF conventions for PHP](conventions--php)
--   [IxDF conventions for Laravel](conventions--laravel)
+-   [IxDF conventions for PHP](conventions--php.md)
+-   [IxDF conventions for Laravel](conventions--laravel.md)
 -   [Clean Code Principles for PHP](clean-code-php.md)
 -   [S.O.L.I.D. Principles for PHP](SOLID.md)
--   [Literature](literature)
+-   [Literature](literature.md)
 
 🦄

library/frontend/README.md

@@ -2,12 +2,12 @@
 
 ## Table of Contents
 
--   [IxDF conventions for JavaScript](conventions--js)
--   [IxDF conventions for JSDoc](conventions--jsdoc)
--   [IxDF conventions for Vue](conventions--vuejs)
--   [IxDF conventions for CSS](conventions--css)
+-   [IxDF conventions for JavaScript](conventions--js.md)
+-   [IxDF conventions for JSDoc](conventions--jsdoc.md)
+-   [IxDF conventions for Vue](conventions--vuejs.md)
+-   [IxDF conventions for CSS](conventions--css.md)
 -   [Clean Code Principles for JavaScript](clean-code-js.md)
--   [Literature](conventions--css)
+-   [Literature](conventions--css.md)
 -   [#UseThePlatform](use-the-platform.md)
 
 🦄