add fontsUrlHash to options to avoid adding extra hash parameters to url function

[nasserghiasi]

This is very useful when a developer wants to build icons through the webpack build process or git hooks and commit the output. But in the current state of the repository developers, cant prevent adding hash parameters to the output CSS or SCSS file and on each running of build those parameters will change and developers should be careful about that changes and revert them. So this is annoying.

Before: @font-face { font-family: $icons-font; src: url('./icon-font.woff2?6b5eab133ec268cf9627ede6bfc39908') format('woff2'), url('./icon-font.woff?6b5eab133ec268cf9627ede6bfc39908') format('woff'); }

After: @font-face { font-family: $icons-font; src: url('./icon-font.woff2?') format('woff2'), url('./icon-font.woff?') format('woff'); }

[vaceslav]

Any Progress on this PR? It is exactly my problem now. :-)