Added free Dutch programming books for Java and PHP (#4397)

* Added free Dutch programming courses for Java and PHP

* Added free Dutch programming books for Java and PHP

* Added free Dutch programming courses for Java and PHP

* Added free Dutch programming books for Java and PHP

free-programming-books-nl.md

 ### Index
 
+* [Java](#java)
 * [PHP](#php)
   * [Symfony](#symfony)
 * [Python](#python)
 * [Scratch](#scratch)
 
 
+### Java
+
+* [Programmeren in Java](https://nl.wikibooks.org/wiki/Programmeren_in_Java) (Wikibooks)
+
+
 ### PHP
 
+* [Programmeren in PHP](https://nl.wikibooks.org/wiki/Programmeren_in_PHP) (Wikibooks)
+
+
 #### Symfony
 
 * [Symfony 5: Snel van start](https://symfony.com/doc/current/the-fast-track/nl/index.html)