Add support for "none" category

[nick-ls]

Resolves #2656

---
title: Syntax Highlighting
category: none
---

With navigation.includeCategories being set to true, this will place the markdown file at the top level of navigation:

[Gerrit0]

Awesome! I thought it was going to be a pretty easy update. Could you make the same addition to the groups section of the navigation builder?

[nick-ls]

/**
 * Calculates the square root of a number.
 *
 * @group None
 */
export function sqrt(x: number): number;

Setting the group to none with navigation.includeGroups now places that group at the top level of navigation.

[Gerrit0]

Thanks!