Update "Symfony: The Fast Track" book

[bkosun]

What does this PR do?

Add resource(s)

IMPORTANT

• [x] Read our contributing guidelines.
• [x] Is this a revision of a previously submitted PR? If so, STOP! Go back, reopen the PR, and add commit(s) the branch you previously submitted. Please don't make the job of reviewing more difficult by hiding previous work.

For resources

Description

Update "Symfony 5: The Fast Track" book.

Why is this valuable (or not)?

This book shows developers the power of the framework and how it can improve their productivity.

How do we know it's really free?

This book is written by the Symfony author (Fabien Potencier) and is hosted on the Symfony official website.

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

It is a book.

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

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

[bkosun]

@eshellman, Please note that these are two different books, and the content varies depending on the Symfony version.

The official website provides links to both editions: https://symfony.com/book

Regarding using a link to the current version, I read the contribution guidelines before submitting a PR. However, in this case, this could lead to unexpected situations, since, for example, after the book is released for the next Symfony version, the link would point to the new edition instead of the expected one. Unfortunately, there is no permanent (current) link to a specific edition.

We could have left only the most current revision, but major versions do not guarantee compatibility, and the content may not be up-to-date. That's why two editions are provided instead of one.

The archive links have been updated according to these notes, and this does not affect the currentness of the book's content, even if the snapshot is older than the previous one.

[eshellman]

The big advantage of "current" links for us is that they should work even if you don't come back to update them. It should not be our job to track versions. please follow the recommendations given.

[bkosun]

@eshellman, I understand why you prefer "current" links, but in this case, it won't work as you expect for the reason I described above. Using "current" links will eventually result in the user seeing content that isn't expected. Furthermore, versions 5.4 and 6.4 are final releases and won't be changed in the future.

[eshellman]

asking for review