support latest release of parcel bundler

MarkdownAsset.js

@@ -4,18 +4,11 @@ const marked = require('marked');
 module.exports = class MarkdownAsset extends HTMLAsset {
     constructor(name, pkg, options) {
         super(name, pkg, options);
-        this.type = 'js';
         this.markedOptions = pkg.marked || {}
     }
 
     parse(code) {
         this.contents = marked(code, this.markedOptions);
         return super.parse(this.contents);
     }
-
-    generate() {
-        return {
-            js: `module.exports=\`${super.generate()}\``
-        };
-    }
 }