RFC: Support for @typeparam or @template for documenting generic parameters

In https://github.com/Microsoft/tsdoc/issues/8#issuecomment-424751850 @aciccarello wrote:

For a generic type definition, it can be helpful to document what the generic type is used for. Using @template was mentioned in some previous comments but I wonder if @typeparam would be better. Either way, I think this would be a good candidate for inclusion of the standard tags.

VS Code already has some support for @template and there has been a request for TypeDoc to support that as well (TypeStrong/typedoc#860). TypeDoc currently supports @typeparam T - Description and @param <T> - Description.

/**
 * Alias for array
 * 
 * @typeparam T - Type of objects the list contains
 */
type List<T> = Array<T>;

/**
 * Wrapper for an HTTP Response
 * @typeparam B - Response body
 * @param <H> - Headers
 */
interface HttpResponse<B, H> {
    body: B;
    headers: H;
    statusCode: number;
}

Start by reviewing the linked TSDoc issue #8 discussion and the TypeDoc #860 reference, then compare the @typeparam, @template, and @param examples in this issue. Determine the standard syntax and semantics for generic-parameter documentation; done requires an agreed RFC direction rather than a localized edit.