Add German book C-HowTo for language C

[jk4e]

What does this PR do?

Add a resource: Add a German book for language C

For resources

Description

Free online tutorial for learning the C programming language in the German language. This is an online version of the printed form. The C-HowTo is a manual for a practical introduction to C programming,

Why is this valuable (or not)?

I read it myself when I was a C beginner. It's great and very clearly written. Highly recommended for C beginners or general programming beginners who want to learn their first language.

How do we know it's really free?

First sentence on the website : "This is a free online manual for learning the C programming language." (translate from German in English). The website has been created by the author himself.

For book lists, is it a book? For course lists, is it a course? etc.

It says tutorial, but it is just a free online version of the printed/physical book, which you can buy online if you like. Type: Book (HTML)

Checklist:

• [x] Read our contributing guidelines.
• [x] Search for duplicates.
• [x] Include author(s) and platform where appropriate.
• [x] Put lists in alphabetical order, correct spacing.
• [x] Add needed indications (PDF, access notes, under construction).
• [x] Used an informative name for this pull request.

Follow-up

• Check the status of GitHub Actions and resolve any reported warnings!

[github-actions[bot]]

Linter failed, fix the error(s):

  free-programming-books/books/free-programming-books-de.md
  69:3-69:88  warning  Remove trailing slash (https://www.c-howto.de)  no-url-trailing-slash  remark-lint

[eshellman]

Thanks, and welcome to free-programming-books!