Added Laravel, Bootstrap into free-programming-books-zh.md (#4304)

* Added Laravel, Bootstrap into free-programming-books-zh.md

* Moved Bootstrap from single resource to HTML/CSS

* Added author to Bootstrap 4

* fix alphabetical ordering problem

free-programming-books-zh.md

@@ -60,6 +60,7 @@
   * [NoSQL](#nosql)
   * [Perl](#perl)
   * [PHP](#php)
+    * [Laravel](#laravel)
     * [Symfony](#symfony)
   * [PostgreSQL](#postgresql)
   * [Python](#python)
@@ -417,6 +418,7 @@
 
 ### HTML / CSS
 
+* [Bootstrap 4 繁體中文手冊](https://bootstrap.hexschool.com) - 六角學院
 * [CSS3 Tutorial 《CSS3 教程》](https://github.com/waylau/css3-tutorial)
 * [CSS参考手册](http://css.doyoe.com)
 * [Emmet 文档](http://yanxyz.github.io/emmet-docs/)
@@ -608,18 +610,25 @@
 ### PHP
 
 * [Composer中文文档](http://docs.phpcomposer.com)
-* [Laravel5.4中文文档](http://d.laravel-china.org/docs/5.4)
 * [Phalcon7中文文档](http://www.myleftstudio.com)
 * [PHP 之道](http://wulijun.github.io/php-the-right-way/)
 * [PHP中文手册](http://php.net/manual/zh/)
 * [PHP标准规范中文版](https://psr.phphub.org)
-* [Symfony2 实例教程](https://wusuopu.gitbooks.io/symfony2_tutorial/content)
 * [Yii2中文文档](http://www.yiichina.com/doc/guide/2.0)
 * [深入理解 PHP 内核](http://www.php-internals.com/book/)
 
 
+#### Laravel
+
+* [Laravel 5.4 中文文档](http://d.laravel-china.org/docs/5.4)
+* [Laravel 6 中文文档](https://learnku.com/docs/laravel/6.x)
+* [Laravel 7 中文文档](https://learnku.com/docs/laravel/7.x)
+* [Laravel 8 中文文档](https://learnku.com/docs/laravel/8.x)
+
+
 #### Symfony
 
+* [Symfony 2 实例教程](https://wusuopu.gitbooks.io/symfony2_tutorial/content)
 * [Symfony 5 快速开发](https://symfony.com/doc/5.0/the-fast-track/zh_CN/index.html)