How to use env/config variables in frontmatter in .md files?

[victor-ponamariov]

I use meta attributes in the frontmatter section.

I need to specify full URL of my site for images, not a relative one as I do now
content: "/img/forms-in-modals-case/social.png

But I cannot figure out how to get something like content: $config.public.websiteUrl + '/img/forms-in-modals-case/social.png'