handle multiple font names in css var

Former-commit-id: ab906019f6a585c7ac44004645c9461cfb7533b6

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

@@ -72,10 +72,11 @@ this.singlefile.lib.modules.fontsMinifier = this.singlefile.lib.modules.fontsMin
 					const matchedVar = familyName.match(/^var\((--.*)\)$/);
 					if (matchedVar && matchedVar[1]) {
 						const computedFamilyName = getComputedStyle.call(window, options.doc.body).getPropertyValue(matchedVar[1]);
-						return computedFamilyName || familyName;
+						return (computedFamilyName && computedFamilyName.split(",").map(name => getFontFamily(name))) || familyName;
 					}
 					return familyName;
 				}));
+				fontsInfo.used = fontsInfo.used.map(fontNames => fontNames.flat());
 			}
 			const variableFound = fontsInfo.used.find(fontNames => fontNames.find(fontName => fontName.startsWith("var(--")));
 			let unusedFonts, filteredUsedFonts;