Content proposal in C# (fr) and Spring (en)

[C-Alexis4414]

What does this PR do?

Added C# and Spring learning resources.

For resources

Description

For C# courses, it's a playlist on the Pentiminax channel.
And for the books on Spring, there are several PDFs on the Baeldung site.

Why is this valuable (or not)?

It is useful for learning object-oriented programming in a dotNET environment or in Java with the Spring framework.

How do we know it's really free?

Yes it's free.
For PDFs on Spring, you must enter your email address to receive them.

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

Checklist:

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

Follow-up

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

[github-actions]

Linter failed, fix the error(s):

free-programming-books/books/free-programming-books-langs.md
1098:1-1103:101  warning  Alphabetical ordering: swap l.1103 and l.1102  alphabetize-lists  remark-lint

free-programming-books/courses/free-courses-fr.md
52:1-53:107  warning  Alphabetical ordering: swap l.53 and l.52  alphabetize-lists  remark-lint

[PiousSutherland]

This:

* [Software Architecture with Spring 5.0](https://www.packtpub.com/free-ebooks/software-architecture-spring-50) - René Enríquez, Alberto Salazar (Packt account *required*)
* [Spring Framework Cookbook: Hot Recipes for Spring Framework](https://www.javacodegeeks.com/wp-content/uploads/2017/01/Spring-Framework-Cookbook.pdf) - JCGs (Java Code Geeks) (PDF)
* [Spring Framework Notes for Professionals](https://goalkicker.com/SpringFrameworkBook) - Compiled from StackOverflow documentation (PDF)
* [Spring Framework Reference Documentation](https://docs.spring.io/spring/docs/current/spring-framework-reference/) - Rod Johnson, et al.
* [Spring books and guides](https://www.baeldung.com/baeldung-ebooks) - Baeldung (PDF sent by email)

Needs to change to this (alphabtical):

* [Software Architecture with Spring 5.0](https://www.packtpub.com/free-ebooks/software-architecture-spring-50) - René Enríquez, Alberto Salazar (Packt account *required*)
* [Spring books and guides](https://www.baeldung.com/baeldung-ebooks) - Baeldung (PDF sent by email)
* [Spring Framework Cookbook: Hot Recipes for Spring Framework](https://www.javacodegeeks.com/wp-content/uploads/2017/01/Spring-Framework-Cookbook.pdf) - JCGs (Java Code Geeks) (PDF)
* [Spring Framework Notes for Professionals](https://goalkicker.com/SpringFrameworkBook) - Compiled from StackOverflow documentation (PDF)
* [Spring Framework Reference Documentation](https://docs.spring.io/spring/docs/current/spring-framework-reference/) - Rod Johnson, et al.

[eshellman]

We do not accept listings for books sent with email.

[PiousSutherland]

This:

* [C# - Cours](https://www.youtube.com/playlist?list=PLrSOXFDHBtfGBHAMEg9Om9nF_7R7h5mO7) - Formation Video
* [Apprendre le C#](https://www.youtube.com/playlist?list=PLkHw7J3J2iapWFUnQmVzsRCU5YxaAWHSY) - Pentiminax

Changes to:

* [Apprendre le C#](https://www.youtube.com/playlist?list=PLkHw7J3J2iapWFUnQmVzsRCU5YxaAWHSY) - Pentiminax
* [C# - Cours](https://www.youtube.com/playlist?list=PLrSOXFDHBtfGBHAMEg9Om9nF_7R7h5mO7) - Formation Video

[C-Alexis4414]

I corrected the order in the French courses for references in C# and I removed the reference to the books on Spring.

[eshellman]

Thanks, and welcome to free-programming-books!