editorconfig autocomplete for roslyn settings

It would be awesome if the C# extension could add auto-complete options for the C#-specific editorconfig settings. The [editor config](https://marketplace.visualstudio.com/items?itemName=EditorConfig.EditorConfig) plugin only provides autocomplete a few, basic options.

```ini
# Examples
[*.cs]
dotnet_sort_system_directives_first = true:warning
csharp_style_var_for_built_in_types = true:suggestion
csharp_style_expression_bodied_methods = false:none
```

See also https://github.com/dotnet/roslyn/blob/master/.editorconfig
https://docs.microsoft.com/en-us/visualstudio/ide/editorconfig-code-style-settings-reference