Small typo in the documentation for the YamlConfigProvider

[MatthijsPrent]

https://github.com/fsprojects/FSharp.Configuration/blob/2ac7103314b5b01fe5cd9565feb18d69491dc115/docs/content/YamlConfigProvider.fsx#L146

And, of course, we now able to access all the config data in a nice typed way like this:

suggested change to:

And, of course, we are now able to access all the config data in a nice typed way like this:

[sergey-tihon]

Please open pull request if you want propose changes