Allow to optionally define website copyright holder name and url usin…

[raubvogel]

…g site.copyright and site.copyright_url

This is an enhancement or feature.

Summary

In https://github.com/mmistakes/so-simple-theme you can edit the copyright statement by using the site.copyright variable. In https://github.com/mmistakes/minimal-mistakes it is hardcoded in _includes/footer.html to use the site.url and site.title.

The proposed change modifies _includes/footer.html and creates two variables -- site.copyright_url and site.copyright -- which if defined, say

title: My Awesome site
copyright: I did it
copyright_url: "https://example.com"

use them instead. Note that neither need to exist: one can have site.copyright_url without site.copyright or vice-versa.

Context

This is not related to any GitHub issue at all.