prevent removing local() functions in font face src

lib/single-file/css-fonts-minifier.js

@@ -25,7 +25,7 @@ this.fontsMinifier = this.fontsMinifier || (() => {
 	const REGEXP_URL_SIMPLE_QUOTES_FN = /url\s*\(\s*'(.*?)'\s*\)/i;
 	const REGEXP_URL_DOUBLE_QUOTES_FN = /url\s*\(\s*"(.*?)"\s*\)/i;
 	const REGEXP_URL_NO_QUOTES_FN = /url\s*\(\s*(.*?)\s*\)/i;
-	const REGEXP_URL_FUNCTION = /url\(.*?\)\s*(,|$)/g;
+	const REGEXP_URL_FUNCTION = /(url|local)\(.*?\)\s*(,|$)/g;
 	const REGEXP_COMMA = /\s*,\s*/;
 	const REGEXP_DASH = /-/;
 	const REGEXP_QUESTION_MARK = /\?/g;
@@ -231,7 +231,7 @@ this.fontsMinifier = this.fontsMinifier || (() => {
 		}
 		if (!woffFontFound) {
 			woffFontFound = fontSources.find(fontSource => fontTest(fontSource, "woff"));
-		}		
+		}
 		stats.fonts.processed += fontSources.length;
 		stats.fonts.discarded += fontSources.length;
 		if (woffFontFound) {