Add variable to font path

[rafaeldev]

What does this PR do?

• Add flexibility to change font serve path

How should this be manually tested?

• Build and run it

Any background context you want to provide?

This change was motivated by new rails asset pipeline. When we put summernote font to be served from sprockets, the font path can't be reach

Rails.application.config.assets.paths << Rails.root.join("node_modules/summernote/dist/font")

Files start being served from http://localhost:3000/assets/font-name.tff

With this change, we can set the server folder on our scss file, like this:

$sni-font-path: ".";

Thanks!

[DennisSuitters]

Thank you for your contribution. I'm pretty sure there used to be a SASS variable doing the same thing in the past. Not sure why that was changed.