Enabling font features / alternative glyph variants

[WieeRd]

Great thing about Fira Code is that it provides a rich set of font features, allowing you to nitpick the minor details and customize them to your likings.

https://github.com/tonsky/FiraCode/wiki/How-to-enable-stylistic-sets

It would be great if Ligatured Hack can inherit these font features and retain the customizability.

[WieeRd]

Related: ToxicFrog/Ligaturizer#88