Enable and document code snippet links

Summary: ^

Reviewed By: nikoant

Differential Revision: D30573928

fbshipit-source-id: 6b0a15d565b2c65891762e141b19d6bed14a9673

website/docusaurus.config.js

@@ -188,6 +188,9 @@ const siteConfig = {
       },
     ],
   ],
+  customFields: {
+    fbRepoName: 'fbsource',
+  },
   // end_config_example
   plugins: [
     './src/plugins/support-symlinks',