No docs for ResourceKind, ResourceKindProperty

The only currently [available doc](https://azure.github.io/typespec-azure/docs/howtos/ARM/resource-type#resourcekind) mentions an obsolete model ResourceKind:

```typespec
model EmployeeResource is TrackedResource {
@doc("The employee name, using 'Firstname Lastname' notation")
@segment("employees")
@key("employeeName")
@visibility("read")
@path
name: string;

...ResourceKind;
}
```

Using which produces a warning:

>Deprecated: `ResourceKind` will be deprecated. Please use `ResourceKindProperty` instead.

Also it says the following:

>For more information on user experiences in the Azure Portal, see [Portal Support](https://eng.ms/docs/products/arm/rpaas/portal/gettingstarted)

The link it points to doesn't mention `kind`. I'm not sure if `kind` is necessarily related to Portal Experience. For example, Azure Functions and Logic Apps are differentiated from regular Web Apps by kind what has nothing to do with UX.

Searching for either `ResourceKind` or `ResourceKindProperty` doesn't yield any meaningful results:

1. https://github.com/search?q=repo%3AAzure%2Fazure-rest-api-specs+ResourceKind+path%3Atsp&type=code
2. https://github.com/search?q=repo%3AAzure%2Fazure-rest-api-specs-pr+ResourceKind+path%3Atsp&type=code

Start with the ARM resource-type documentation page linked in the issue and compare its ResourceKind example with the current ResourceKindProperty name. Search the linked azure-rest-api-specs TypeSpec results and the Portal Support page for usage and meaning of kind. Done means the docs cover ResourceKindProperty and accurately explain or remove the unsupported Portal Support guidance.

Written by the indexing model from the issue text.