fix(core): update

ts/index.ts

@@ -16,6 +16,7 @@ export class SmartMarkdown {
       headingStyle: 'atx',
       codeBlockStyle: 'fenced'
     });
+    turndownInstance.use(plugins.turndownPluginGfm.gfm);
     return turndownInstance.turndown(htmlString);
   }
 }

ts/smartmarkdown.plugins.ts

@@ -1,4 +1,5 @@
 import marked = require('marked');
 import turndown from 'turndown';
+import * as turndownPluginGfm from 'turndown-plugin-gfm';
 
-export { marked, turndown };
+export { marked, turndown, turndownPluginGfm };