An attempt to fix the preview

	modified:   docusaurus.config.js
	new file:   static/img/preview.jpg

Author: abernatskiy

docusaurus.config.js

@@ -106,6 +106,7 @@ const config = {
 
       //... other Algolia params
     },
+    image: 'img/preview.jpg'
   }),
 
   plugins: [