Added 'Learn Git the Hard Way' book to Git sectin

[HarisTechWerk]

• Added 'Learn Git the Hard Way' book under the Git section.
• This is a valuable resource for learning Git in-depth.

[github-actions]

Linter failed, fix the error(s):

free-programming-books/books/free-programming-books-langs.md
           1:1  warning  Missing newline character at end of file                               final-newline          remark-lint
2713:1-2714:76  warning  Incorrect number of blank lines between last section and next heading  blank-lines-1-0-2      remark-lint
 2716:1-2716:8  warning  Incorrect number of blank lines between heading and section            blank-lines-1-0-2      remark-lint
2717:3-2717:64  warning  Remove trailing slash (https://learn-git-the-hard-way.com)             no-url-trailing-slash  remark-lint