About pOS - missing links

https://documentation.platformos.com/developer-guide/about-platformos/about-platformos

Missing links to:

- [Official YAML Documentation](http://www.yaml.org/start.html) is missing
- Learn more - explore [our documentation topics on using GraphQL in platformOS](https://documentation.platformos.com/developer-guide/graphql/developing-graphql-queries-using-graphiql) - doesnt work