Fix broken external link in docs (#18)

README.md

@@ -184,7 +184,7 @@ have sensitive information.
 #### WrapFunc (default: `nil`)
 
 If this value is default (which is `nil`), `go-apperrors` will use the lib
-[github.com/go-errors/errors](github.com/go-errors/errors) to wrap and attach stack trace to errors.
+[github.com/go-errors/errors](https://github.com/go-errors/errors) to wrap and attach stack trace to errors.
 If you don't want to attach stack trace, provide a self-implementation on initialization.
 
 ```go