Implement font-variant-ligatures.

https://developer.mozilla.org/en/docs/Web/CSS/font-variant-ligatures
https://www.w3.org/TR/css-fonts-3/#font-variant-ligatures-prop

lib/extract/extractText.js

@@ -54,6 +54,7 @@ export function extractFont(props) {
         letterSpacing,
         wordSpacing,
         kerning,
+        fontVariantLigatures,
     } = props;
     let {
         fontSize,
@@ -76,6 +77,7 @@ export function extractFont(props) {
         letterSpacing,
         wordSpacing,
         kerning,
+        fontVariantLigatures,
     }, prop => !_.isNil(prop));
 
     if (typeof font === 'string') {