Fix invalid font-display value (#148)

* fixing invalid font-display value

* Fix invalid font-display value

Author: Ravi Kumar Hamsa

src/__tests__/fixtures/expected.js

@@ -32,7 +32,7 @@ export const fallbackLookup = {
 };
 
 export const fontFaces =
-  '\n@font-face {font-family: "Lato-Regular"; font-display: \'fallback\'; src: url("Lato-Regular.woff") format("woff")\n,url("Lato-Regular.woff2") format("woff2")\n;}\n@font-face {font-family: "Lato-Bold"; font-display: \'fallback\'; src: url("Lato-Bold.woff") format("woff")\n,url("Lato-Bold.woff2") format("woff2")\n;}\n@font-face {font-family: "Lato-Thin"; font-display: \'fallback\'; src: url("Lato-Thin.woff") format("woff")\n,url("Lato-Thin.woff2") format("woff2")\n;}';
+  '\n@font-face {font-family: "Lato-Regular"; font-display: fallback; src: url("Lato-Regular.woff") format("woff")\n,url("Lato-Regular.woff2") format("woff2")\n;}\n@font-face {font-family: "Lato-Bold"; font-display: fallback; src: url("Lato-Bold.woff") format("woff")\n,url("Lato-Bold.woff2") format("woff2")\n;}\n@font-face {font-family: "Lato-Thin"; font-display: fallback; src: url("Lato-Thin.woff") format("woff")\n,url("Lato-Thin.woff2") format("woff2")\n;}';
 
 export const preloadLinks =
   '\n<link rel="preload" href="Lato-Regular.woff2" as="font" type="font/woff2" crossorigin>';

src/generate-font-faces.js

@@ -12,7 +12,7 @@ export default function generateFontFaces(fontDictionary: {}) {
     const font = fontDictionary[fontName];
     if (font) {
       faces.push(
-        `@font-face {font-family: "${fontName}"; font-display: 'fallback'; src: ${String(
+        `@font-face {font-family: "${fontName}"; font-display: fallback; src: ${String(
           asFontFaceSrc(font.urls)
         )};}`
       );