fix potential loading issue

should only add one preload for each font, as multiple preload will cause multiple downloads

Author: laysent

README.md

@@ -73,8 +73,8 @@ plugins: [
 
 When preloading files, the plugin will use different `as` attribute depends on the type of each
 file. For each file ends with `.css`, the plugin will preload it with `as=style`, for each file ends
-with `.woff`, `.woff2`, `.eot`, `.otf` or `.ttf`, the plugin will preload it with `as=font`, while
-for all other files, `as=script` will be used.
+with `.woff2`, the plugin will preload it with `as=font`, while for all other files, `as=script`
+will be used.
 
 If you do not prefer to determine `as` attribute depends on suffix of filename, you can also
 explicitly name it using `as`:
@@ -100,6 +100,7 @@ plugins: [
     rel: 'preload',
     as(entry) {
       if (/\.css$/.test(entry)) return 'style';
+      if (/\.woff$/.test(entry)) return 'font';
       if (/\.png$/.test(entry)) return 'image';
       return 'script';
     }

index.js

@@ -76,7 +76,7 @@ class PreloadPlugin {
             let asValue;
             if (!options.as) {
               if (entry.match(/\.css$/)) asValue = 'style';
-              else if (entry.match(/\.(?:eot|otf|ttf|woff2?)$/)) asValue = 'font';
+              else if (entry.match(/\.woff2$/)) asValue = 'font';
               else asValue = 'script';
             } else if (typeof options.as === 'function') {
               asValue = options.as(entry);