Add image formats to Faker\Provider\Image

[calebdw]

What is the reason for this PR?

The placeholder.com API allows for a few image formats, whereas image() and imageUrl() in Faker\Provider\Image defaulted to png.

• Slight feature extension

Author's checklist

• Follow the Contribution Guide
• New features and changes are documented - PR #66

Summary of changes

Added a static array to Faker\Provider\Image which contains allowable image formats (per Placeholder). Appended $format argument to both Image::image() and Image::imageUrl() which defaults to 'png'. Throw an exception in Image::imageUrl() if an invalid format is received. Wrote unit tests for all the image formats and IllegalArgumentException.

Review checklist

• All checks have passed
• Changes are approved by maintainer

[pimjansen]

Phpcs is failing. Can you review?

[calebdw]

I fixed the above issues, but I am unable to run phpcs myself since I have PHP 8.1 installed on my system.

[pimjansen]

I fixed the above issues, but I am unable to run phpcs myself since I have PHP 8.1 installed on my system.

Pipeline is green, will do final review tomorrow so we can merge

[pimjansen]

LGTM

[jderusse]

Adding a method in an interface is a BC break.
This PR should have been released in a Major version.

[DvDty]

Adding a method in an interface is a BC break. This PR should have been released in a Major version.

Interesting, there is a job in the pipeline that checks for backwards compatibility and it has passed for the current pull request: https://github.com/FakerPHP/Faker/actions/runs/2293913195