update Chinese resources

update `free-programming-books-zh.md`:

* added new categories: **Erlang**, **R**, **Scheme**, **Vim**
* added new resources in several categories
* reconstructed the architecture of the file: created a new **section** *”语言无关“* (*Language Agnostic*), and listed *“在线教育"* (*Online Education*), *"软件开发方法"* (*Software Developing*) , *"操作系统"* (*Operation System*), etc. as **subsections** under *"语言无关"* (*Language Agnostic*)
* fixed an invalid link in the contents