Feature request - add a built-in yaml validator that also checks included yamls

### Installed product versions
Visual Studio 2015  14.0.25431.01 Update 3
Gitlab extension 1.0369

### Description
Is it possible to add a yaml validator like the one exists in the VScode extension?
I can't find a YAML validator that knows what to do with `imported` yaml files.
example: 

```
include:
    - ".imported_config1.yml"
    - ".imported_config2.yml"
```