Update free-programming-books-langs.md

[MrCyGuy]

What does this PR do?

Add resource(s) | Remove resource(s) | Add info | Improve repo

I added resources

For resources

Description

Added a section on CSS and also contributed to additions in Arduino, Java, C, and Basic.

Why is this valuable (or not)?

This gives people a chance to learn more about CSS and have extended knowledge from other more popular mediums.

How do we know it's really free?

Without prior purchases or information imputing, I can read what I have added, so others should be able to as well.

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

All of what I added were books.

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
    420:1-424:3  warning  Incorrect number of blank lines between last section and next heading  blank-lines-1-0-2  remark-lint
1056:1-1101:141  warning  Alphabetical ordering: swap l.1059 and l.1058                          alphabetize-lists  remark-lint
1056:1-1101:141  warning  Alphabetical ordering: swap l.1096 and l.1095                          alphabetize-lists  remark-lint