Add support for AVIF image in site health

[itzmekhokan]

Summary

Fixes #1152

Relevant technical choices

Adds a module in site health to check for AVIF image format is support and shows a warning if support is not present.
If server has AVIF support, the AVIF support warning is not shown.

Screenshot

[github-actions]

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Co-authored-by: itzmekhokan <khokansardar@git.wordpress.org>
Co-authored-by: mukeshpanchal27 <mukesh27@git.wordpress.org>
Co-authored-by: westonruter <westonruter@git.wordpress.org>
Co-authored-by: adamsilverstein <adamsilverstein@git.wordpress.org>

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[westonruter]

LGTM

[mukeshpanchal27]

Thanks @itzmekhokan for the PR! Left some nit-pick.

[itzmekhokan]

Thanks @itzmekhokan for the PR! Left some nit-pick.

@mukeshpanchal27 Updated the points.