chore: Improve metadata about Flutter in Action by Eric Windmill

[davorpa]

What does this PR do?

Add info | Improve repo

For resources

Description

Why is this valuable (or not)?

Improves metadata and resource format via backlog task #5762 since was added at #6575

• Use top most domain url
• - as title and author separator
• Some Maning online books has a time chapters read limit and after that sign up is needed. Therefore a note about it have been added.

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)

Follow-up

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