Add ffmpeg

[danvergara]

Add ffmpeg

Description

This PR introduces ffmpeg as a dependency to handle image, instead of std or experimental package to do the encoding. This means Morphos will relay on the ffmpeg installed on the host machine. Since the only way of distribution is a container image, the dependency is already installed on the image. This had a good side and it was that I could add support for AVIF.

I'll work on adding support for HEIF/HEIF, despite there's not support for them from ffmpeg yet. I'll give a libheif a new try, since I use Debian Trixie as a final stage in my container image and libheif on that base image isn't that behind.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Added new tests cases and QA'd the container image to convert images.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have checked my code and corrected any misspellings