[Feature Request]: Provide a checkbox for a project's commercial use

[s3nnet]

Feature Description

This one is inspired by #1710.
Commercial use limits the scope of suitable licenses for (Featured) Images. Therefore, there should IMHO be a simple checkbox providing that piece of important information in the site settings, so that Publii can properly react to this fact, e.g. in the context of a built-in downloader for libre images, fonts being used, themes, and generally all licence-encumbered material.

[dziudek]

I do not get the idea of adding any separate UI for handling such things and we won't implement such changes. The only issue to solve which I see is to use {{{ x }}} for featured image credits instead of {{ x }} so links will work also for WYSIWYG editor with featured images