Release 4.0.0-rc9

• Enhance Font Awesome version 4 compatibility: add shimming of the version 4 font-family to enable
  version 4 icons defined as pseudo-elements to be rendered via the version of Font Awesome 5 loaded
  by this plugin.

• Add warnings to the admin UI to indicate that using svg and pseudo-elements may result in slow
  performance, and that svg with pseudo-elements and version 4 compatibility is not supported at all.