Make compatible with Rails 7

[cseelus]

Simple update to the gemspec file, to make font-awesome-rails compatible with Rails 7, released December 15, 2021.

Fixes #224

[rmm5t]

Thank you. I'm going to update the CI workflows to make sure we have test coverage, but I'll try to get this merged and released sometime today.

[epugh]

I saw the new release, but not tweaks to the CHANGELOG document, would be nice to see that doc updated as well!

[rmm5t]

@epugh I updated the CHANGELOG for ease/completeness, but GitHub releases have replaced the CHANGELOG:

See GitHub Releases for all future releases

[viviana-aline]

When I import the font-awesome CSS in Rails 7 in application.css with

/*
 *= require font-awesome
 */

as the documentation says, it still doesn't load the CSS (icons are not loading), so it doesn't seem entirely compatible with Rails 7...unless I'm doing something wrong. I tried to import the CSS manually with the old CDN link, and the icons are loading fine.