Fixed broken link in github token missing warning (siddharthkp#352)

Author: iNishant

src/api.js

@@ -17,7 +17,7 @@ else if (ci) {
   // warn(`github token not found
   //
   //   You are missing out on some cool features.
-  //   Read more here: https://github.com/siddharthkp/bundlesize#2-build-status
+  //   Read more here: https://github.com/siddharthkp/bundlesize#build-status-for-github
   // `)
 }