Add FASTAPI info in python section

[colmwoods]

Fixes #12192

What does this PR do?

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

IMPORTANT

• [x] Read our contributing guidelines.
• [x] This is not a revision of a previous PR.

For resources

Description

Adds a new subsection for FastAPI under the Python section with four free and verified learning resources.

Why is this valuable (or not)?

FastAPI is one of the fastest-growing Python frameworks for APIs and backend development. These resources help developers learn and build modern, type-safe Python web applications.

How do we know it's really free?

All included links are to official documentation, GitHub repositories, or free online books/tutorials.

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

It’s a documentation and tutorial list (not paid or third-party gated content).

Checklist:

• [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

GitHub Actions should pass without warnings.

[github-actions[bot]]

Linter failed, fix the error(s):

free-programming-books/books/free-programming-books-langs.md
2147:1-2150:95  warning  Alphabetical ordering: swap l.2150 and l.2149         alphabetize-lists      remark-lint
2147:3-2147:57  warning  Remove trailing slash (https://fastapi.tiangolo.com)  no-url-trailing-slash  remark-lint

[github-actions[bot]]

Linter failed, fix the error(s):

free-programming-books/books/free-programming-books-langs.md
  172:5-180:26  warning  Alphabetical ordering: swap l.174 and l.173    alphabetize-lists  remark-lint
2149:1-2152:96  warning  Alphabetical ordering: swap l.2150 and l.2149  alphabetize-lists  remark-lint

[github-actions[bot]]

Linter failed, fix the error(s):

free-programming-books/books/free-programming-books-langs.md
2141:1-2144:96  warning  Alphabetical ordering: swap l.2142 and l.2141  alphabetize-lists  remark-lint

[github-actions[bot]]

Linter failed, fix the error(s):

free-programming-books/books/free-programming-books-langs.md
2141:1-2143:103  warning  Incorrect number of blank lines between last section and next heading  blank-lines-1-0-2  remark-lint

[eshellman]

no, I mean you should move the existing blue book to this section

[eshellman]

please remove the DSA stuff from this PR. use a separate branch to submit that

[eshellman]

look at the diff, please. You may need to restart with a fresh branch.

[eshellman]

Thanks, and welcome to free-programming-books!